Java tutorial
/* * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.io; import java.util.Formatter; import java.util.Locale; import java.nio.charset.Charset; import java.nio.charset.IllegalCharsetNameException; import java.nio.charset.UnsupportedCharsetException; /** * A {@code PrintStream} adds functionality to another output stream, * namely the ability to print representations of various data values * conveniently. Two other features are provided as well. Unlike other output * streams, a {@code PrintStream} never throws an * {@code IOException}; instead, exceptional situations merely set an * internal flag that can be tested via the {@code checkError} method. * Optionally, a {@code PrintStream} can be created so as to flush * automatically; this means that the {@code flush} method is * automatically invoked after a byte array is written, one of the * {@code println} methods is invoked, or a newline character or byte * ({@code '\n'}) is written. * * <p> All characters printed by a {@code PrintStream} are converted into * bytes using the given encoding or charset, or platform's default character * encoding if not specified. * The {@link PrintWriter} class should be used in situations that require * writing characters rather than bytes. * * <p> This class always replaces malformed and unmappable character sequences with * the charset's default replacement string. * The {@linkplain java.nio.charset.CharsetEncoder} class should be used when more * control over the encoding process is required. * * @author Frank Yellin * @author Mark Reinhold * @since 1.0 */ public class PrintStream extends FilterOutputStream implements Appendable, Closeable { private final boolean autoFlush; private boolean trouble = false; private Formatter formatter; /** * Track both the text- and character-output streams, so that their buffers * can be flushed without flushing the entire stream. */ private BufferedWriter textOut; private OutputStreamWriter charOut; /** * requireNonNull is explicitly declared here so as not to create an extra * dependency on java.util.Objects.requireNonNull. PrintStream is loaded * early during system initialization. */ private static <T> T requireNonNull(T obj, String message) { if (obj == null) throw new NullPointerException(message); return obj; } /** * Returns a charset object for the given charset name. * @throws NullPointerException is csn is null * @throws UnsupportedEncodingException if the charset is not supported */ private static Charset toCharset(String csn) throws UnsupportedEncodingException { requireNonNull(csn, "charsetName"); try { return Charset.forName(csn); } catch (IllegalCharsetNameException | UnsupportedCharsetException unused) { // UnsupportedEncodingException should be thrown throw new UnsupportedEncodingException(csn); } } /* Private constructors */ private PrintStream(boolean autoFlush, OutputStream out) { super(out); this.autoFlush = autoFlush; this.charOut = new OutputStreamWriter(this); this.textOut = new BufferedWriter(charOut); } /* Variant of the private constructor so that the given charset name * can be verified before evaluating the OutputStream argument. Used * by constructors creating a FileOutputStream that also take a * charset name. */ private PrintStream(boolean autoFlush, Charset charset, OutputStream out) { this(out, autoFlush, charset); } /** * Creates a new print stream. This stream will not flush automatically. * * @param out The output stream to which values and objects will be * printed * * @see java.io.PrintWriter#PrintWriter(java.io.OutputStream) */ public PrintStream(OutputStream out) { this(out, false); } /** * Creates a new print stream. * * @param out The output stream to which values and objects will be * printed * @param autoFlush A boolean; if true, the output buffer will be flushed * whenever a byte array is written, one of the * {@code println} methods is invoked, or a newline * character or byte ({@code '\n'}) is written * * @see java.io.PrintWriter#PrintWriter(java.io.OutputStream, boolean) */ public PrintStream(OutputStream out, boolean autoFlush) { this(autoFlush, requireNonNull(out, "Null output stream")); } /** * Creates a new print stream. * * @param out The output stream to which values and objects will be * printed * @param autoFlush A boolean; if true, the output buffer will be flushed * whenever a byte array is written, one of the * {@code println} methods is invoked, or a newline * character or byte ({@code '\n'}) is written * @param encoding The name of a supported * <a href="../lang/package-summary.html#charenc"> * character encoding</a> * * @throws UnsupportedEncodingException * If the named encoding is not supported * * @since 1.4 */ public PrintStream(OutputStream out, boolean autoFlush, String encoding) throws UnsupportedEncodingException { this(requireNonNull(out, "Null output stream"), autoFlush, toCharset(encoding)); } /** * Creates a new print stream, with the specified OutputStream, automatic line * flushing and charset. This convenience constructor creates the necessary * intermediate {@link java.io.OutputStreamWriter OutputStreamWriter}, * which will encode characters using the provided charset. * * @param out The output stream to which values and objects will be * printed * @param autoFlush A boolean; if true, the output buffer will be flushed * whenever a byte array is written, one of the * {@code println} methods is invoked, or a newline * character or byte ({@code '\n'}) is written * @param charset A {@linkplain java.nio.charset.Charset charset} * * @since 10 */ public PrintStream(OutputStream out, boolean autoFlush, Charset charset) { super(out); this.autoFlush = autoFlush; this.charOut = new OutputStreamWriter(this, charset); this.textOut = new BufferedWriter(charOut); } /** * Creates a new print stream, without automatic line flushing, with the * specified file name. This convenience constructor creates * the necessary intermediate {@link java.io.OutputStreamWriter * OutputStreamWriter}, which will encode characters using the * {@linkplain java.nio.charset.Charset#defaultCharset() default charset} * for this instance of the Java virtual machine. * * @param fileName * The name of the file to use as the destination of this print * stream. If the file exists, then it will be truncated to * zero size; otherwise, a new file will be created. The output * will be written to the file and is buffered. * * @throws FileNotFoundException * If the given file object does not denote an existing, writable * regular file and a new regular file of that name cannot be * created, or if some other error occurs while opening or * creating the file * * @throws SecurityException * If a security manager is present and {@link * SecurityManager#checkWrite checkWrite(fileName)} denies write * access to the file * * @since 1.5 */ public PrintStream(String fileName) throws FileNotFoundException { this(false, new FileOutputStream(fileName)); } /** * Creates a new print stream, without automatic line flushing, with the * specified file name and charset. This convenience constructor creates * the necessary intermediate {@link java.io.OutputStreamWriter * OutputStreamWriter}, which will encode characters using the provided * charset. * * @param fileName * The name of the file to use as the destination of this print * stream. If the file exists, then it will be truncated to * zero size; otherwise, a new file will be created. The output * will be written to the file and is buffered. * * @param csn * The name of a supported {@linkplain java.nio.charset.Charset * charset} * * @throws FileNotFoundException * If the given file object does not denote an existing, writable * regular file and a new regular file of that name cannot be * created, or if some other error occurs while opening or * creating the file * * @throws SecurityException * If a security manager is present and {@link * SecurityManager#checkWrite checkWrite(fileName)} denies write * access to the file * * @throws UnsupportedEncodingException * If the named charset is not supported * * @since 1.5 */ public PrintStream(String fileName, String csn) throws FileNotFoundException, UnsupportedEncodingException { // ensure charset is checked before the file is opened this(false, toCharset(csn), new FileOutputStream(fileName)); } /** * Creates a new print stream, without automatic line flushing, with the * specified file name and charset. This convenience constructor creates * the necessary intermediate {@link java.io.OutputStreamWriter * OutputStreamWriter}, which will encode characters using the provided * charset. * * @param fileName * The name of the file to use as the destination of this print * stream. If the file exists, then it will be truncated to * zero size; otherwise, a new file will be created. The output * will be written to the file and is buffered. * * @param charset * A {@linkplain java.nio.charset.Charset charset} * * @throws IOException * if an I/O error occurs while opening or creating the file * * @throws SecurityException * If a security manager is present and {@link * SecurityManager#checkWrite checkWrite(fileName)} denies write * access to the file * * @since 10 */ public PrintStream(String fileName, Charset charset) throws IOException { this(false, requireNonNull(charset, "charset"), new FileOutputStream(fileName)); } /** * Creates a new print stream, without automatic line flushing, with the * specified file. This convenience constructor creates the necessary * intermediate {@link java.io.OutputStreamWriter OutputStreamWriter}, * which will encode characters using the {@linkplain * java.nio.charset.Charset#defaultCharset() default charset} for this * instance of the Java virtual machine. * * @param file * The file to use as the destination of this print stream. If the * file exists, then it will be truncated to zero size; otherwise, * a new file will be created. The output will be written to the * file and is buffered. * * @throws FileNotFoundException * If the given file object does not denote an existing, writable * regular file and a new regular file of that name cannot be * created, or if some other error occurs while opening or * creating the file * * @throws SecurityException * If a security manager is present and {@link * SecurityManager#checkWrite checkWrite(file.getPath())} * denies write access to the file * * @since 1.5 */ public PrintStream(File file) throws FileNotFoundException { this(false, new FileOutputStream(file)); } /** * Creates a new print stream, without automatic line flushing, with the * specified file and charset. This convenience constructor creates * the necessary intermediate {@link java.io.OutputStreamWriter * OutputStreamWriter}, which will encode characters using the provided * charset. * * @param file * The file to use as the destination of this print stream. If the * file exists, then it will be truncated to zero size; otherwise, * a new file will be created. The output will be written to the * file and is buffered. * * @param csn * The name of a supported {@linkplain java.nio.charset.Charset * charset} * * @throws FileNotFoundException * If the given file object does not denote an existing, writable * regular file and a new regular file of that name cannot be * created, or if some other error occurs while opening or * creating the file * * @throws SecurityException * If a security manager is present and {@link * SecurityManager#checkWrite checkWrite(file.getPath())} * denies write access to the file * * @throws UnsupportedEncodingException * If the named charset is not supported * * @since 1.5 */ public PrintStream(File file, String csn) throws FileNotFoundException, UnsupportedEncodingException { // ensure charset is checked before the file is opened this(false, toCharset(csn), new FileOutputStream(file)); } /** * Creates a new print stream, without automatic line flushing, with the * specified file and charset. This convenience constructor creates * the necessary intermediate {@link java.io.OutputStreamWriter * OutputStreamWriter}, which will encode characters using the provided * charset. * * @param file * The file to use as the destination of this print stream. If the * file exists, then it will be truncated to zero size; otherwise, * a new file will be created. The output will be written to the * file and is buffered. * * @param charset * A {@linkplain java.nio.charset.Charset charset} * * @throws IOException * if an I/O error occurs while opening or creating the file * * @throws SecurityException * If a security manager is present and {@link * SecurityManager#checkWrite checkWrite(file.getPath())} * denies write access to the file * * @since 10 */ public PrintStream(File file, Charset charset) throws IOException { this(false, requireNonNull(charset, "charset"), new FileOutputStream(file)); } /** Check to make sure that the stream has not been closed */ private void ensureOpen() throws IOException { if (out == null) throw new IOException("Stream closed"); } /** * Flushes the stream. This is done by writing any buffered output bytes to * the underlying output stream and then flushing that stream. * * @see java.io.OutputStream#flush() */ public void flush() { synchronized (this) { try { ensureOpen(); out.flush(); } catch (IOException x) { trouble = true; } } } private boolean closing = false; /* To avoid recursive closing */ /** * Closes the stream. This is done by flushing the stream and then closing * the underlying output stream. * * @see java.io.OutputStream#close() */ public void close() { synchronized (this) { if (!closing) { closing = true; try { textOut.close(); out.close(); } catch (IOException x) { trouble = true; } textOut = null; charOut = null; out = null; } } } /** * Flushes the stream and checks its error state. The internal error state * is set to {@code true} when the underlying output stream throws an * {@code IOException} other than {@code InterruptedIOException}, * and when the {@code setError} method is invoked. If an operation * on the underlying output stream throws an * {@code InterruptedIOException}, then the {@code PrintStream} * converts the exception back into an interrupt by doing: * <pre>{@code * Thread.currentThread().interrupt(); * }</pre> * or the equivalent. * * @return {@code true} if and only if this stream has encountered an * {@code IOException} other than * {@code InterruptedIOException}, or the * {@code setError} method has been invoked */ public boolean checkError() { if (out != null) flush(); if (out instanceof java.io.PrintStream) { PrintStream ps = (PrintStream) out; return ps.checkError(); } return trouble; } /** * Sets the error state of the stream to {@code true}. * * <p> This method will cause subsequent invocations of {@link * #checkError()} to return {@code true} until * {@link #clearError()} is invoked. * * @since 1.1 */ protected void setError() { trouble = true; } /** * Clears the internal error state of this stream. * * <p> This method will cause subsequent invocations of {@link * #checkError()} to return {@code false} until another write * operation fails and invokes {@link #setError()}. * * @since 1.6 */ protected void clearError() { trouble = false; } /* * Exception-catching, synchronized output operations, * which also implement the write() methods of OutputStream */ /** * Writes the specified byte to this stream. If the byte is a newline and * automatic flushing is enabled then the {@code flush} method will be * invoked. * * <p> Note that the byte is written as given; to write a character that * will be translated according to the platform's default character * encoding, use the {@code print(char)} or {@code println(char)} * methods. * * @param b The byte to be written * @see #print(char) * @see #println(char) */ public void write(int b) { try { synchronized (this) { ensureOpen(); out.write(b); if ((b == '\n') && autoFlush) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } } /** * Writes {@code len} bytes from the specified byte array starting at * offset {@code off} to this stream. If automatic flushing is * enabled then the {@code flush} method will be invoked. * * <p> Note that the bytes will be written as given; to write characters * that will be translated according to the platform's default character * encoding, use the {@code print(char)} or {@code println(char)} * methods. * * @param buf A byte array * @param off Offset from which to start taking bytes * @param len Number of bytes to write */ public void write(byte buf[], int off, int len) { try { synchronized (this) { ensureOpen(); out.write(buf, off, len); if (autoFlush) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } } /* * The following private methods on the text- and character-output streams * always flush the stream buffers, so that writes to the underlying byte * stream occur as promptly as with the original PrintStream. */ private void write(char[] buf) { try { synchronized (this) { ensureOpen(); textOut.write(buf); textOut.flushBuffer(); charOut.flushBuffer(); if (autoFlush) { for (int i = 0; i < buf.length; i++) if (buf[i] == '\n') { out.flush(); break; } } } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } } // Used to optimize away back-to-back flushing and synchronization when // using println, but since subclasses could exist which depend on // observing a call to print followed by newLine() we only use this if // getClass() == PrintStream.class to avoid compatibility issues. private void writeln(char[] buf) { try { synchronized (this) { ensureOpen(); textOut.write(buf); textOut.newLine(); textOut.flushBuffer(); charOut.flushBuffer(); if (autoFlush) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } } private void write(String s) { try { synchronized (this) { ensureOpen(); textOut.write(s); textOut.flushBuffer(); charOut.flushBuffer(); if (autoFlush && (s.indexOf('\n') >= 0)) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } } // Used to optimize away back-to-back flushing and synchronization when // using println, but since subclasses could exist which depend on // observing a call to print followed by newLine we only use this if // getClass() == PrintStream.class to avoid compatibility issues. private void writeln(String s) { try { synchronized (this) { ensureOpen(); textOut.write(s); textOut.newLine(); textOut.flushBuffer(); charOut.flushBuffer(); if (autoFlush) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } } private void newLine() { try { synchronized (this) { ensureOpen(); textOut.newLine(); textOut.flushBuffer(); charOut.flushBuffer(); if (autoFlush) out.flush(); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } } /* Methods that do not terminate lines */ /** * Prints a boolean value. The string produced by {@link * java.lang.String#valueOf(boolean)} is translated into bytes * according to the platform's default character encoding, and these bytes * are written in exactly the manner of the * {@link #write(int)} method. * * @param b The {@code boolean} to be printed */ public void print(boolean b) { write(String.valueOf(b)); } /** * Prints a character. The character is translated into one or more bytes * according to the platform's default character encoding, and these bytes * are written in exactly the manner of the * {@link #write(int)} method. * * @param c The {@code char} to be printed */ public void print(char c) { write(String.valueOf(c)); } /** * Prints an integer. The string produced by {@link * java.lang.String#valueOf(int)} is translated into bytes * according to the platform's default character encoding, and these bytes * are written in exactly the manner of the * {@link #write(int)} method. * * @param i The {@code int} to be printed * @see java.lang.Integer#toString(int) */ public void print(int i) { write(String.valueOf(i)); } /** * Prints a long integer. The string produced by {@link * java.lang.String#valueOf(long)} is translated into bytes * according to the platform's default character encoding, and these bytes * are written in exactly the manner of the * {@link #write(int)} method. * * @param l The {@code long} to be printed * @see java.lang.Long#toString(long) */ public void print(long l) { write(String.valueOf(l)); } /** * Prints a floating-point number. The string produced by {@link * java.lang.String#valueOf(float)} is translated into bytes * according to the platform's default character encoding, and these bytes * are written in exactly the manner of the * {@link #write(int)} method. * * @param f The {@code float} to be printed * @see java.lang.Float#toString(float) */ public void print(float f) { write(String.valueOf(f)); } /** * Prints a double-precision floating-point number. The string produced by * {@link java.lang.String#valueOf(double)} is translated into * bytes according to the platform's default character encoding, and these * bytes are written in exactly the manner of the {@link * #write(int)} method. * * @param d The {@code double} to be printed * @see java.lang.Double#toString(double) */ public void print(double d) { write(String.valueOf(d)); } /** * Prints an array of characters. The characters are converted into bytes * according to the platform's default character encoding, and these bytes * are written in exactly the manner of the * {@link #write(int)} method. * * @param s The array of chars to be printed * * @throws NullPointerException If {@code s} is {@code null} */ public void print(char s[]) { write(s); } /** * Prints a string. If the argument is {@code null} then the string * {@code "null"} is printed. Otherwise, the string's characters are * converted into bytes according to the platform's default character * encoding, and these bytes are written in exactly the manner of the * {@link #write(int)} method. * * @param s The {@code String} to be printed */ public void print(String s) { write(String.valueOf(s)); } /** * Prints an object. The string produced by the {@link * java.lang.String#valueOf(Object)} method is translated into bytes * according to the platform's default character encoding, and these bytes * are written in exactly the manner of the * {@link #write(int)} method. * * @param obj The {@code Object} to be printed * @see java.lang.Object#toString() */ public void print(Object obj) { write(String.valueOf(obj)); } /* Methods that do terminate lines */ /** * Terminates the current line by writing the line separator string. The * line separator string is defined by the system property * {@code line.separator}, and is not necessarily a single newline * character ({@code '\n'}). */ public void println() { newLine(); } /** * Prints a boolean and then terminate the line. This method behaves as * though it invokes {@link #print(boolean)} and then * {@link #println()}. * * @param x The {@code boolean} to be printed */ public void println(boolean x) { if (getClass() == PrintStream.class) { writeln(String.valueOf(x)); } else { synchronized (this) { print(x); newLine(); } } } /** * Prints a character and then terminate the line. This method behaves as * though it invokes {@link #print(char)} and then * {@link #println()}. * * @param x The {@code char} to be printed. */ public void println(char x) { if (getClass() == PrintStream.class) { writeln(String.valueOf(x)); } else { synchronized (this) { print(x); newLine(); } } } /** * Prints an integer and then terminate the line. This method behaves as * though it invokes {@link #print(int)} and then * {@link #println()}. * * @param x The {@code int} to be printed. */ public void println(int x) { if (getClass() == PrintStream.class) { writeln(String.valueOf(x)); } else { synchronized (this) { print(x); newLine(); } } } /** * Prints a long and then terminate the line. This method behaves as * though it invokes {@link #print(long)} and then * {@link #println()}. * * @param x a The {@code long} to be printed. */ public void println(long x) { if (getClass() == PrintStream.class) { writeln(String.valueOf(x)); } else { synchronized (this) { print(x); newLine(); } } } /** * Prints a float and then terminate the line. This method behaves as * though it invokes {@link #print(float)} and then * {@link #println()}. * * @param x The {@code float} to be printed. */ public void println(float x) { if (getClass() == PrintStream.class) { writeln(String.valueOf(x)); } else { synchronized (this) { print(x); newLine(); } } } /** * Prints a double and then terminate the line. This method behaves as * though it invokes {@link #print(double)} and then * {@link #println()}. * * @param x The {@code double} to be printed. */ public void println(double x) { if (getClass() == PrintStream.class) { writeln(String.valueOf(x)); } else { synchronized (this) { print(x); newLine(); } } } /** * Prints an array of characters and then terminate the line. This method * behaves as though it invokes {@link #print(char[])} and * then {@link #println()}. * * @param x an array of chars to print. */ public void println(char[] x) { if (getClass() == PrintStream.class) { writeln(x); } else { synchronized (this) { print(x); newLine(); } } } /** * Prints a String and then terminate the line. This method behaves as * though it invokes {@link #print(String)} and then * {@link #println()}. * * @param x The {@code String} to be printed. */ public void println(String x) { if (getClass() == PrintStream.class) { writeln(String.valueOf(x)); } else { synchronized (this) { print(x); newLine(); } } } /** * Prints an Object and then terminate the line. This method calls * at first String.valueOf(x) to get the printed object's string value, * then behaves as * though it invokes {@link #print(String)} and then * {@link #println()}. * * @param x The {@code Object} to be printed. */ public void println(Object x) { String s = String.valueOf(x); if (getClass() == PrintStream.class) { // need to apply String.valueOf again since first invocation // might return null writeln(String.valueOf(s)); } else { synchronized (this) { print(s); newLine(); } } } /** * A convenience method to write a formatted string to this output stream * using the specified format string and arguments. * * <p> An invocation of this method of the form * {@code out.printf(format, args)} behaves * in exactly the same way as the invocation * * <pre>{@code * out.format(format, args) * }</pre> * * @param format * A format string as described in <a * href="../util/Formatter.html#syntax">Format string syntax</a> * * @param args * Arguments referenced by the format specifiers in the format * string. If there are more arguments than format specifiers, the * extra arguments are ignored. The number of arguments is * variable and may be zero. The maximum number of arguments is * limited by the maximum dimension of a Java array as defined by * <cite>The Java™ Virtual Machine Specification</cite>. * The behaviour on a * {@code null} argument depends on the <a * href="../util/Formatter.html#syntax">conversion</a>. * * @throws java.util.IllegalFormatException * If a format string contains an illegal syntax, a format * specifier that is incompatible with the given arguments, * insufficient arguments given the format string, or other * illegal conditions. For specification of all possible * formatting errors, see the <a * href="../util/Formatter.html#detail">Details</a> section of the * formatter class specification. * * @throws NullPointerException * If the {@code format} is {@code null} * * @return This output stream * * @since 1.5 */ public PrintStream printf(String format, Object... args) { return format(format, args); } /** * A convenience method to write a formatted string to this output stream * using the specified format string and arguments. * * <p> An invocation of this method of the form * {@code out.printf(l, format, args)} behaves * in exactly the same way as the invocation * * <pre>{@code * out.format(l, format, args) * }</pre> * * @param l * The {@linkplain java.util.Locale locale} to apply during * formatting. If {@code l} is {@code null} then no localization * is applied. * * @param format * A format string as described in <a * href="../util/Formatter.html#syntax">Format string syntax</a> * * @param args * Arguments referenced by the format specifiers in the format * string. If there are more arguments than format specifiers, the * extra arguments are ignored. The number of arguments is * variable and may be zero. The maximum number of arguments is * limited by the maximum dimension of a Java array as defined by * <cite>The Java™ Virtual Machine Specification</cite>. * The behaviour on a * {@code null} argument depends on the <a * href="../util/Formatter.html#syntax">conversion</a>. * * @throws java.util.IllegalFormatException * If a format string contains an illegal syntax, a format * specifier that is incompatible with the given arguments, * insufficient arguments given the format string, or other * illegal conditions. For specification of all possible * formatting errors, see the <a * href="../util/Formatter.html#detail">Details</a> section of the * formatter class specification. * * @throws NullPointerException * If the {@code format} is {@code null} * * @return This output stream * * @since 1.5 */ public PrintStream printf(Locale l, String format, Object... args) { return format(l, format, args); } /** * Writes a formatted string to this output stream using the specified * format string and arguments. * * <p> The locale always used is the one returned by {@link * java.util.Locale#getDefault(Locale.Category)} with * {@link java.util.Locale.Category#FORMAT FORMAT} category specified, * regardless of any previous invocations of other formatting methods on * this object. * * @param format * A format string as described in <a * href="../util/Formatter.html#syntax">Format string syntax</a> * * @param args * Arguments referenced by the format specifiers in the format * string. If there are more arguments than format specifiers, the * extra arguments are ignored. The number of arguments is * variable and may be zero. The maximum number of arguments is * limited by the maximum dimension of a Java array as defined by * <cite>The Java™ Virtual Machine Specification</cite>. * The behaviour on a * {@code null} argument depends on the <a * href="../util/Formatter.html#syntax">conversion</a>. * * @throws java.util.IllegalFormatException * If a format string contains an illegal syntax, a format * specifier that is incompatible with the given arguments, * insufficient arguments given the format string, or other * illegal conditions. For specification of all possible * formatting errors, see the <a * href="../util/Formatter.html#detail">Details</a> section of the * formatter class specification. * * @throws NullPointerException * If the {@code format} is {@code null} * * @return This output stream * * @since 1.5 */ public PrintStream format(String format, Object... args) { try { synchronized (this) { ensureOpen(); if ((formatter == null) || (formatter.locale() != Locale.getDefault(Locale.Category.FORMAT))) formatter = new Formatter((Appendable) this); formatter.format(Locale.getDefault(Locale.Category.FORMAT), format, args); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } return this; } /** * Writes a formatted string to this output stream using the specified * format string and arguments. * * @param l * The {@linkplain java.util.Locale locale} to apply during * formatting. If {@code l} is {@code null} then no localization * is applied. * * @param format * A format string as described in <a * href="../util/Formatter.html#syntax">Format string syntax</a> * * @param args * Arguments referenced by the format specifiers in the format * string. If there are more arguments than format specifiers, the * extra arguments are ignored. The number of arguments is * variable and may be zero. The maximum number of arguments is * limited by the maximum dimension of a Java array as defined by * <cite>The Java™ Virtual Machine Specification</cite>. * The behaviour on a * {@code null} argument depends on the <a * href="../util/Formatter.html#syntax">conversion</a>. * * @throws java.util.IllegalFormatException * If a format string contains an illegal syntax, a format * specifier that is incompatible with the given arguments, * insufficient arguments given the format string, or other * illegal conditions. For specification of all possible * formatting errors, see the <a * href="../util/Formatter.html#detail">Details</a> section of the * formatter class specification. * * @throws NullPointerException * If the {@code format} is {@code null} * * @return This output stream * * @since 1.5 */ public PrintStream format(Locale l, String format, Object... args) { try { synchronized (this) { ensureOpen(); if ((formatter == null) || (formatter.locale() != l)) formatter = new Formatter(this, l); formatter.format(l, format, args); } } catch (InterruptedIOException x) { Thread.currentThread().interrupt(); } catch (IOException x) { trouble = true; } return this; } /** * Appends the specified character sequence to this output stream. * * <p> An invocation of this method of the form {@code out.append(csq)} * behaves in exactly the same way as the invocation * * <pre>{@code * out.print(csq.toString()) * }</pre> * * <p> Depending on the specification of {@code toString} for the * character sequence {@code csq}, the entire sequence may not be * appended. For instance, invoking then {@code toString} method of a * character buffer will return a subsequence whose content depends upon * the buffer's position and limit. * * @param csq * The character sequence to append. If {@code csq} is * {@code null}, then the four characters {@code "null"} are * appended to this output stream. * * @return This output stream * * @since 1.5 */ public PrintStream append(CharSequence csq) { print(String.valueOf(csq)); return this; } /** * Appends a subsequence of the specified character sequence to this output * stream. * * <p> An invocation of this method of the form * {@code out.append(csq, start, end)} when * {@code csq} is not {@code null}, behaves in * exactly the same way as the invocation * * <pre>{@code * out.print(csq.subSequence(start, end).toString()) * }</pre> * * @param csq * The character sequence from which a subsequence will be * appended. If {@code csq} is {@code null}, then characters * will be appended as if {@code csq} contained the four * characters {@code "null"}. * * @param start * The index of the first character in the subsequence * * @param end * The index of the character following the last character in the * subsequence * * @return This output stream * * @throws IndexOutOfBoundsException * If {@code start} or {@code end} are negative, {@code start} * is greater than {@code end}, or {@code end} is greater than * {@code csq.length()} * * @since 1.5 */ public PrintStream append(CharSequence csq, int start, int end) { if (csq == null) csq = "null"; return append(csq.subSequence(start, end)); } /** * Appends the specified character to this output stream. * * <p> An invocation of this method of the form {@code out.append(c)} * behaves in exactly the same way as the invocation * * <pre>{@code * out.print(c) * }</pre> * * @param c * The 16-bit character to append * * @return This output stream * * @since 1.5 */ public PrintStream append(char c) { print(c); return this; } }