Java tutorial
/* * Copyright (c) 2003, 2019, 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.lang; import jdk.internal.HotSpotIntrinsicCandidate; /** * A mutable sequence of characters. This class provides an API compatible * with {@code StringBuffer}, but with no guarantee of synchronization. * This class is designed for use as a drop-in replacement for * {@code StringBuffer} in places where the string buffer was being * used by a single thread (as is generally the case). Where possible, * it is recommended that this class be used in preference to * {@code StringBuffer} as it will be faster under most implementations. * * <p>The principal operations on a {@code StringBuilder} are the * {@code append} and {@code insert} methods, which are * overloaded so as to accept data of any type. Each effectively * converts a given datum to a string and then appends or inserts the * characters of that string to the string builder. The * {@code append} method always adds these characters at the end * of the builder; the {@code insert} method adds the characters at * a specified point. * <p> * For example, if {@code z} refers to a string builder object * whose current contents are "{@code start}", then * the method call {@code z.append("le")} would cause the string * builder to contain "{@code startle}", whereas * {@code z.insert(4, "le")} would alter the string builder to * contain "{@code starlet}". * <p> * In general, if sb refers to an instance of a {@code StringBuilder}, * then {@code sb.append(x)} has the same effect as * {@code sb.insert(sb.length(), x)}. * <p> * Every string builder has a capacity. As long as the length of the * character sequence contained in the string builder does not exceed * the capacity, it is not necessary to allocate a new internal * buffer. If the internal buffer overflows, it is automatically made larger. * * <p>Instances of {@code StringBuilder} are not safe for * use by multiple threads. If such synchronization is required then it is * recommended that {@link java.lang.StringBuffer} be used. * * <p>Unless otherwise noted, passing a {@code null} argument to a constructor * or method in this class will cause a {@link NullPointerException} to be * thrown. * * @apiNote * {@code StringBuilder} implements {@code Comparable} but does not override * {@link Object#equals equals}. Thus, the natural ordering of {@code StringBuilder} * is inconsistent with equals. Care should be exercised if {@code StringBuilder} * objects are used as keys in a {@code SortedMap} or elements in a {@code SortedSet}. * See {@link Comparable}, {@link java.util.SortedMap SortedMap}, or * {@link java.util.SortedSet SortedSet} for more information. * * @author Michael McCloskey * @see java.lang.StringBuffer * @see java.lang.String * @since 1.5 */ public final class StringBuilder extends AbstractStringBuilder implements java.io.Serializable, Comparable<StringBuilder>, CharSequence { /** use serialVersionUID for interoperability */ static final long serialVersionUID = 4383685877147921099L; /** * Constructs a string builder with no characters in it and an * initial capacity of 16 characters. */ @HotSpotIntrinsicCandidate public StringBuilder() { super(16); } /** * Constructs a string builder with no characters in it and an * initial capacity specified by the {@code capacity} argument. * * @param capacity the initial capacity. * @throws NegativeArraySizeException if the {@code capacity} * argument is less than {@code 0}. */ @HotSpotIntrinsicCandidate public StringBuilder(int capacity) { super(capacity); } /** * Constructs a string builder initialized to the contents of the * specified string. The initial capacity of the string builder is * {@code 16} plus the length of the string argument. * * @param str the initial contents of the buffer. */ @HotSpotIntrinsicCandidate public StringBuilder(String str) { super(str); } /** * Constructs a string builder that contains the same characters * as the specified {@code CharSequence}. The initial capacity of * the string builder is {@code 16} plus the length of the * {@code CharSequence} argument. * * @param seq the sequence to copy. */ public StringBuilder(CharSequence seq) { super(seq); } /** * Compares two {@code StringBuilder} instances lexicographically. This method * follows the same rules for lexicographical comparison as defined in the * {@linkplain java.lang.CharSequence#compare(java.lang.CharSequence, * java.lang.CharSequence) CharSequence.compare(this, another)} method. * * <p> * For finer-grained, locale-sensitive String comparison, refer to * {@link java.text.Collator}. * * @param another the {@code StringBuilder} to be compared with * * @return the value {@code 0} if this {@code StringBuilder} contains the same * character sequence as that of the argument {@code StringBuilder}; a negative integer * if this {@code StringBuilder} is lexicographically less than the * {@code StringBuilder} argument; or a positive integer if this {@code StringBuilder} * is lexicographically greater than the {@code StringBuilder} argument. * * @since 11 */ @Override public int compareTo(StringBuilder another) { return super.compareTo(another); } @Override public StringBuilder append(Object obj) { return append(String.valueOf(obj)); } @Override @HotSpotIntrinsicCandidate public StringBuilder append(String str) { super.append(str); return this; } /** * Appends the specified {@code StringBuffer} to this sequence. * <p> * The characters of the {@code StringBuffer} argument are appended, * in order, to this sequence, increasing the * length of this sequence by the length of the argument. * If {@code sb} is {@code null}, then the four characters * {@code "null"} are appended to this sequence. * <p> * Let <i>n</i> be the length of this character sequence just prior to * execution of the {@code append} method. Then the character at index * <i>k</i> in the new character sequence is equal to the character at * index <i>k</i> in the old character sequence, if <i>k</i> is less than * <i>n</i>; otherwise, it is equal to the character at index <i>k-n</i> * in the argument {@code sb}. * * @param sb the {@code StringBuffer} to append. * @return a reference to this object. */ public StringBuilder append(StringBuffer sb) { super.append(sb); return this; } @Override public StringBuilder append(CharSequence s) { super.append(s); return this; } /** * @throws IndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder append(CharSequence s, int start, int end) { super.append(s, start, end); return this; } @Override public StringBuilder append(char[] str) { super.append(str); return this; } /** * @throws IndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder append(char[] str, int offset, int len) { super.append(str, offset, len); return this; } @Override public StringBuilder append(boolean b) { super.append(b); return this; } @Override @HotSpotIntrinsicCandidate public StringBuilder append(char c) { super.append(c); return this; } @Override @HotSpotIntrinsicCandidate public StringBuilder append(int i) { super.append(i); return this; } @Override public StringBuilder append(long lng) { super.append(lng); return this; } @Override public StringBuilder append(float f) { super.append(f); return this; } @Override public StringBuilder append(double d) { super.append(d); return this; } /** * @since 1.5 */ @Override public StringBuilder appendCodePoint(int codePoint) { super.appendCodePoint(codePoint); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder delete(int start, int end) { super.delete(start, end); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder deleteCharAt(int index) { super.deleteCharAt(index); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder replace(int start, int end, String str) { super.replace(start, end, str); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int index, char[] str, int offset, int len) { super.insert(index, str, offset, len); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, Object obj) { super.insert(offset, obj); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, String str) { super.insert(offset, str); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, char[] str) { super.insert(offset, str); return this; } /** * @throws IndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int dstOffset, CharSequence s) { super.insert(dstOffset, s); return this; } /** * @throws IndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int dstOffset, CharSequence s, int start, int end) { super.insert(dstOffset, s, start, end); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, boolean b) { super.insert(offset, b); return this; } /** * @throws IndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, char c) { super.insert(offset, c); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, int i) { super.insert(offset, i); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, long l) { super.insert(offset, l); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, float f) { super.insert(offset, f); return this; } /** * @throws StringIndexOutOfBoundsException {@inheritDoc} */ @Override public StringBuilder insert(int offset, double d) { super.insert(offset, d); return this; } @Override public int indexOf(String str) { return super.indexOf(str); } @Override public int indexOf(String str, int fromIndex) { return super.indexOf(str, fromIndex); } @Override public int lastIndexOf(String str) { return super.lastIndexOf(str); } @Override public int lastIndexOf(String str, int fromIndex) { return super.lastIndexOf(str, fromIndex); } @Override public StringBuilder reverse() { super.reverse(); return this; } @Override @HotSpotIntrinsicCandidate public String toString() { // Create a copy, don't share the array return isLatin1() ? StringLatin1.newString(value, 0, count) : StringUTF16.newString(value, 0, count); } /** * Save the state of the {@code StringBuilder} instance to a stream * (that is, serialize it). * * @serialData the number of characters currently stored in the string * builder ({@code int}), followed by the characters in the * string builder ({@code char[]}). The length of the * {@code char} array may be greater than the number of * characters currently stored in the string builder, in which * case extra characters are ignored. */ private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { s.defaultWriteObject(); s.writeInt(count); char[] val = new char[capacity()]; if (isLatin1()) { StringLatin1.getChars(value, 0, count, val, 0); } else { StringUTF16.getChars(value, 0, count, val, 0); } s.writeObject(val); } /** * readObject is called to restore the state of the StringBuffer from * a stream. */ private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { s.defaultReadObject(); count = s.readInt(); char[] val = (char[]) s.readObject(); initBytes(val, 0, val.length); } }