Centers a String in a larger String of size size using the space character (' '). If the size is less than the String length, the String is returned. - Java java.lang

Description

Centers a String in a larger String of size size using the space character (' '). If the size is less than the String length, the String is returned.

Demo Code

/*//from  w ww  .  ja v  a  2  s .c  om
 * Copyright 2013 Guidewire Software, Inc.
 */
/**
 * This class is based, in part, on org.apache.commons.lang.StringUtils and is intended
 * to break the dependency on that project.
 *
 * @author <a href="http://jakarta.apache.org/turbine/">Apache Jakarta Turbine</a>
 * @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a>
 * @author Daniel L. Rall
 * @author <a href="mailto:gcoladonato@yahoo.com">Greg Coladonato</a>
 * @author <a href="mailto:ed@apache.org">Ed Korthof</a>
 * @author <a href="mailto:rand_mcneely@yahoo.com">Rand McNeely</a>
 * @author Stephen Colebourne
 * @author <a href="mailto:fredrik@westermarck.com">Fredrik Westermarck</a>
 * @author Holger Krauth
 * @author <a href="mailto:alex@purpletech.com">Alexander Day Chaffee</a>
 * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a>
 * @author Arun Mammen Thomas
 * @author Gary Gregory
 * @author Phil Steitz
 * @author Al Chou
 * @author Michael Davey
 * @author Reuben Sivan
 * @author Chris Hyzer
 *  Johnson

 */
//package com.java2s;

public class Main {
    public static void main(String[] argv) {
        String str = "java2s.com";
        int size = 42;
        System.out.println(center(str, size));
    }

    /**
     * The empty String <code>""</code>.
     * @since 2.0
     */
    public static final String EMPTY = "";
    /**
     * <p>The maximum size to which the padding constant(s) can expand.</p>
     */
    private static final int PAD_LIMIT = 8192;

    /**
     * <p>Centers a String in a larger String of size <code>size</code>
     * using the space character (' ').<p>
     *
     * <p>If the size is less than the String length, the String is returned.
     * A <code>null</code> String returns <code>null</code>.
     * A negative size is treated as zero.</p>
     *
     * <p>Equivalent to <code>center(str, size, " ")</code>.</p>
     *
     * <pre>
     * center(null, *)   = null
     * center("", 4)     = "    "
     * center("ab", -1)  = "ab"
     * center("ab", 4)   = " ab "
     * center("abcd", 2) = "abcd"
     * center("a", 4)    = " a  "
     * </pre>
     *
     * @param str  the String to center, may be null
     * @param size  the int size of new String, negative treated as zero
     * @return centered String, <code>null</code> if null String input
     */
    public static String center(String str, int size) {
        return center(str, size, ' ');
    }

    /**
     * <p>Centers a String in a larger String of size <code>size</code>.
     * Uses a supplied character as the value to pad the String with.</p>
     *
     * <p>If the size is less than the String length, the String is returned.
     * A <code>null</code> String returns <code>null</code>.
     * A negative size is treated as zero.</p>
     *
     * <pre>
     * center(null, *, *)     = null
     * center("", 4, ' ')     = "    "
     * center("ab", -1, ' ')  = "ab"
     * center("ab", 4, ' ')   = " ab"
     * center("abcd", 2, ' ') = "abcd"
     * center("a", 4, ' ')    = " a  "
     * center("a", 4, 'y')    = "yayy"
     * </pre>
     *
     * @param str  the String to center, may be null
     * @param size  the int size of new String, negative treated as zero
     * @param padChar  the character to pad the new String with
     * @return centered String, <code>null</code> if null String input
     * @since 2.0
     */
    public static String center(String str, int size, char padChar) {
        if (str == null || size <= 0) {
            return str;
        }
        int strLen = str.length();
        int pads = size - strLen;
        if (pads <= 0) {
            return str;
        }
        str = leftPad(str, strLen + pads / 2, padChar);
        str = rightPad(str, size, padChar);
        return str;
    }

    /**
     * <p>Centers a String in a larger String of size <code>size</code>.
     * Uses a supplied String as the value to pad the String with.</p>
     *
     * <p>If the size is less than the String length, the String is returned.
     * A <code>null</code> String returns <code>null</code>.
     * A negative size is treated as zero.</p>
     *
     * <pre>
     * center(null, *, *)     = null
     * center("", 4, " ")     = "    "
     * center("ab", -1, " ")  = "ab"
     * center("ab", 4, " ")   = " ab"
     * center("abcd", 2, " ") = "abcd"
     * center("a", 4, " ")    = " a  "
     * center("a", 4, "yz")   = "yayz"
     * center("abc", 7, null) = "  abc  "
     * center("abc", 7, "")   = "  abc  "
     * </pre>
     *
     * @param str  the String to center, may be null
     * @param size  the int size of new String, negative treated as zero
     * @param padStr  the String to pad the new String with, must not be null or empty
     * @return centered String, <code>null</code> if null String input
     * @throws IllegalArgumentException if padStr is <code>null</code> or empty
     */
    public static String center(String str, int size, String padStr) {
        if (str == null || size <= 0) {
            return str;
        }
        if (isEmpty(padStr)) {
            padStr = " ";
        }
        int strLen = str.length();
        int pads = size - strLen;
        if (pads <= 0) {
            return str;
        }
        str = leftPad(str, strLen + pads / 2, padStr);
        str = rightPad(str, size, padStr);
        return str;
    }

    /**
     * Gets a String's length or <code>0</code> if the String is <code>null</code>.
     *
     * @param str
     *            a String or <code>null</code>
     * @return String length or <code>0</code> if the String is <code>null</code>.
     * @since 2.4
     */
    public static int length(String str) {
        return str == null ? 0 : str.length();
    }

    /**
     * <p>Left pad a String with spaces (' ').</p>
     *
     * <p>The String is padded to the size of <code>size</code>.</p>
     *
     * <pre>
     * leftPad(null, *)   = null
     * leftPad("", 3)     = "   "
     * leftPad("bat", 3)  = "bat"
     * leftPad("bat", 5)  = "  bat"
     * leftPad("bat", 1)  = "bat"
     * leftPad("bat", -1) = "bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @return left padded String or original String if no padding is necessary,
     *  <code>null</code> if null String input
     */
    public static String leftPad(String str, int size) {
        return leftPad(str, size, ' ');
    }

    /**
     * <p>Left pad a String with a specified character.</p>
     *
     * <p>Pad to a size of <code>size</code>.</p>
     *
     * <pre>
     * leftPad(null, *, *)     = null
     * leftPad("", 3, 'z')     = "zzz"
     * leftPad("bat", 3, 'z')  = "bat"
     * leftPad("bat", 5, 'z')  = "zzbat"
     * leftPad("bat", 1, 'z')  = "bat"
     * leftPad("bat", -1, 'z') = "bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @param padChar  the character to pad with
     * @return left padded String or original String if no padding is necessary,
     *  <code>null</code> if null String input
     * @since 2.0
     */
    public static String leftPad(String str, int size, char padChar) {
        if (str == null) {
            return null;
        }
        int pads = size - str.length();
        if (pads <= 0) {
            return str; // returns original String when possible
        }
        if (pads > PAD_LIMIT) {
            return leftPad(str, size, String.valueOf(padChar));
        }
        return padding(pads, padChar).concat(str);
    }

    /**
     * <p>Left pad a String with a specified String.</p>
     *
     * <p>Pad to a size of <code>size</code>.</p>
     *
     * <pre>
     * leftPad(null, *, *)      = null
     * leftPad("", 3, "z")      = "zzz"
     * leftPad("bat", 3, "yz")  = "bat"
     * leftPad("bat", 5, "yz")  = "yzbat"
     * leftPad("bat", 8, "yz")  = "yzyzybat"
     * leftPad("bat", 1, "yz")  = "bat"
     * leftPad("bat", -1, "yz") = "bat"
     * leftPad("bat", 5, null)  = "  bat"
     * leftPad("bat", 5, "")    = "  bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @param padStr  the String to pad with, null or empty treated as single space
     * @return left padded String or original String if no padding is necessary,
     *  <code>null</code> if null String input
     */
    public static String leftPad(String str, int size, String padStr) {
        if (str == null) {
            return null;
        }
        if (isEmpty(padStr)) {
            padStr = " ";
        }
        int padLen = padStr.length();
        int strLen = str.length();
        int pads = size - strLen;
        if (pads <= 0) {
            return str; // returns original String when possible
        }
        if (padLen == 1 && pads <= PAD_LIMIT) {
            return leftPad(str, size, padStr.charAt(0));
        }

        if (pads == padLen) {
            return padStr.concat(str);
        } else if (pads < padLen) {
            return padStr.substring(0, pads).concat(str);
        } else {
            char[] padding = new char[pads];
            char[] padChars = padStr.toCharArray();
            for (int i = 0; i < pads; i++) {
                padding[i] = padChars[i % padLen];
            }
            return new String(padding).concat(str);
        }
    }

    /**
     * <p>Right pad a String with spaces (' ').</p>
     *
     * <p>The String is padded to the size of <code>size</code>.</p>
     *
     * <pre>
     * rightPad(null, *)   = null
     * rightPad("", 3)     = "   "
     * rightPad("bat", 3)  = "bat"
     * rightPad("bat", 5)  = "bat  "
     * rightPad("bat", 1)  = "bat"
     * rightPad("bat", -1) = "bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @return right padded String or original String if no padding is necessary,
     *  <code>null</code> if null String input
     */
    public static String rightPad(String str, int size) {
        return rightPad(str, size, ' ');
    }

    /**
     * <p>Right pad a String with a specified character.</p>
     *
     * <p>The String is padded to the size of <code>size</code>.</p>
     *
     * <pre>
     * rightPad(null, *, *)     = null
     * rightPad("", 3, 'z')     = "zzz"
     * rightPad("bat", 3, 'z')  = "bat"
     * rightPad("bat", 5, 'z')  = "batzz"
     * rightPad("bat", 1, 'z')  = "bat"
     * rightPad("bat", -1, 'z') = "bat"
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @param padChar  the character to pad with
     * @return right padded String or original String if no padding is necessary,
     *  <code>null</code> if null String input
     * @since 2.0
     */
    public static String rightPad(String str, int size, char padChar) {
        if (str == null) {
            return null;
        }
        int pads = size - str.length();
        if (pads <= 0) {
            return str; // returns original String when possible
        }
        if (pads > PAD_LIMIT) {
            return rightPad(str, size, String.valueOf(padChar));
        }
        return str.concat(padding(pads, padChar));
    }

    /**
     * <p>Right pad a String with a specified String.</p>
     *
     * <p>The String is padded to the size of <code>size</code>.</p>
     *
     * <pre>
     * rightPad(null, *, *)      = null
     * rightPad("", 3, "z")      = "zzz"
     * rightPad("bat", 3, "yz")  = "bat"
     * rightPad("bat", 5, "yz")  = "batyz"
     * rightPad("bat", 8, "yz")  = "batyzyzy"
     * rightPad("bat", 1, "yz")  = "bat"
     * rightPad("bat", -1, "yz") = "bat"
     * rightPad("bat", 5, null)  = "bat  "
     * rightPad("bat", 5, "")    = "bat  "
     * </pre>
     *
     * @param str  the String to pad out, may be null
     * @param size  the size to pad to
     * @param padStr  the String to pad with, null or empty treated as single space
     * @return right padded String or original String if no padding is necessary,
     *  <code>null</code> if null String input
     */
    public static String rightPad(String str, int size, String padStr) {
        if (str == null) {
            return null;
        }
        if (isEmpty(padStr)) {
            padStr = " ";
        }
        int padLen = padStr.length();
        int strLen = str.length();
        int pads = size - strLen;
        if (pads <= 0) {
            return str; // returns original String when possible
        }
        if (padLen == 1 && pads <= PAD_LIMIT) {
            return rightPad(str, size, padStr.charAt(0));
        }

        if (pads == padLen) {
            return str.concat(padStr);
        } else if (pads < padLen) {
            return str.concat(padStr.substring(0, pads));
        } else {
            char[] padding = new char[pads];
            char[] padChars = padStr.toCharArray();
            for (int i = 0; i < pads; i++) {
                padding[i] = padChars[i % padLen];
            }
            return str.concat(new String(padding));
        }
    }

    /**
     * <p>Checks if a String is empty ("") or null.</p>
     *
     * <pre>
     * StringUtils.isEmpty(null)      = true
     * StringUtils.isEmpty("")        = true
     * StringUtils.isEmpty(" ")       = false
     * StringUtils.isEmpty("bob")     = false
     * StringUtils.isEmpty("  bob  ") = false
     * </pre>
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer trims the String.
     * That functionality is available in isBlank().</p>
     *
     * @param str  the String to check, may be null
     * @return <code>true</code> if the String is empty or null
     */
    public static boolean isEmpty(String str) {
        return str == null || str.length() == 0;
    }

    /**
     * <p>Returns padding using the specified delimiter repeated
     * to a given length.</p>
     *
     * <pre>
     * padding(0, 'e')  = ""
     * padding(3, 'e')  = "eee"
     * padding(-2, 'e') = IndexOutOfBoundsException
     * </pre>
     *
     * <p>Note: this method doesn't not support padding with
     * <a href="http://www.unicode.org/glossary/#supplementary_character">Unicode Supplementary Characters</a>
     * as they require a pair of <code>char</code>s to be represented.
     * If you are needing to support full I18N of your applications
     * consider using {@link #repeat(String, int)} instead.
     * </p>
     *
     * @param repeat  number of times to repeat delim
     * @param padChar  character to repeat
     * @return String with repeated character
     * @throws IndexOutOfBoundsException if <code>repeat &lt; 0</code>
     * @see #repeat(String, int)
     */
    private static String padding(int repeat, char padChar)
            throws IndexOutOfBoundsException {
        if (repeat < 0) {
            throw new IndexOutOfBoundsException(
                    "Cannot pad a negative amount: " + repeat);
        }
        final char[] buf = new char[repeat];
        for (int i = 0; i < buf.length; i++) {
            buf[i] = padChar;
        }
        return new String(buf);
    }

    /**
     * <p>Gets a substring from the specified String avoiding exceptions.</p>
     *
     * <p>A negative start position can be used to start <code>n</code>
     * characters from the end of the String.</p>
     *
     * <p>A <code>null</code> String will return <code>null</code>.
     * An empty ("") String will return "".</p>
     *
     * <pre>
     * substring(null, *)   = null
     * substring("", *)     = ""
     * substring("abc", 0)  = "abc"
     * substring("abc", 2)  = "c"
     * substring("abc", 4)  = ""
     * substring("abc", -2) = "bc"
     * substring("abc", -4) = "abc"
     * </pre>
     *
     * @param str  the String to get the substring from, may be null
     * @param start  the position to start from, negative means
     *  count back from the end of the String by this many characters
     * @return substring from start position, <code>null</code> if null String input
     */
    public static String substring(String str, int start) {
        if (str == null) {
            return null;
        }

        // handle negatives, which means last n characters
        if (start < 0) {
            start = str.length() + start; // remember start is negative
        }

        if (start < 0) {
            start = 0;
        }
        if (start > str.length()) {
            return EMPTY;
        }

        return str.substring(start);
    }

    /**
     * <p>Gets a substring from the specified String avoiding exceptions.</p>
     *
     * <p>A negative start position can be used to start/end <code>n</code>
     * characters from the end of the String.</p>
     *
     * <p>The returned substring starts with the character in the <code>start</code>
     * position and ends before the <code>end</code> position. All position counting is
     * zero-based -- i.e., to start at the beginning of the string use
     * <code>start = 0</code>. Negative start and end positions can be used to
     * specify offsets relative to the end of the String.</p>
     *
     * <p>If <code>start</code> is not strictly to the left of <code>end</code>, ""
     * is returned.</p>
     *
     * <pre>
     * substring(null, *, *)    = null
     * substring("", * ,  *)    = "";
     * substring("abc", 0, 2)   = "ab"
     * substring("abc", 2, 0)   = ""
     * substring("abc", 2, 4)   = "c"
     * substring("abc", 4, 6)   = ""
     * substring("abc", 2, 2)   = ""
     * substring("abc", -2, -1) = "b"
     * substring("abc", -4, 2)  = "ab"
     * </pre>
     *
     * @param str  the String to get the substring from, may be null
     * @param start  the position to start from, negative means
     *  count back from the end of the String by this many characters
     * @param end  the position to end at (exclusive), negative means
     *  count back from the end of the String by this many characters
     * @return substring from start position to end positon,
     *  <code>null</code> if null String input
     */
    public static String substring(String str, int start, int end) {
        if (str == null) {
            return null;
        }

        // handle negatives
        if (end < 0) {
            end = str.length() + end; // remember end is negative
        }
        if (start < 0) {
            start = str.length() + start; // remember start is negative
        }

        // check length next
        if (end > str.length()) {
            end = str.length();
        }

        // if start is greater than end, return ""
        if (start > end) {
            return EMPTY;
        }

        if (start < 0) {
            start = 0;
        }
        if (end < 0) {
            end = 0;
        }

        return str.substring(start, end);
    }
}

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