Compares two Strings, and returns the index at which the Strings begin to differ. - Java java.lang

Java examples for java.lang:String Compare

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Description

Compares two Strings, and returns the index at which the Strings begin to differ.

Demo Code

/*/*from  ww w  .j  ava2s.co m*/
 * 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[] strs = new String[] { "1", "abc", "level", null,
                "java2s.com", "asdf 123" };
        System.out.println(indexOfDifference(strs));
    }

    /**
     * <p>Compares two Strings, and returns the index at which the
     * Strings begin to differ.</p>
     *
     * <p>For example,
     * <code>indexOfDifference("i am a machine", "i am a robot") -> 7</code></p>
     *
     * <pre>
     * indexOfDifference(null, null) = -1
     * indexOfDifference("", "") = -1
     * indexOfDifference("", "abc") = 0
     * indexOfDifference("abc", "") = 0
     * indexOfDifference("abc", "abc") = -1
     * indexOfDifference("ab", "abxyz") = 2
     * indexOfDifference("abcde", "abxyz") = 2
     * indexOfDifference("abcde", "xyz") = 0
     * </pre>
     *
     * @param str1  the first String, may be null
     * @param str2  the second String, may be null
     * @return the index where str2 and str1 begin to differ; -1 if they are equal
     * @since 2.0
     */
    public static int indexOfDifference(String str1, String str2) {
        if (str1 == str2) {
            return -1;
        }
        if (str1 == null || str2 == null) {
            return 0;
        }
        int i;
        for (i = 0; i < str1.length() && i < str2.length(); ++i) {
            if (str1.charAt(i) != str2.charAt(i)) {
                break;
            }
        }
        if (i < str2.length() || i < str1.length()) {
            return i;
        }
        return -1;
    }

    /**
     * <p>Compares all Strings in an array and returns the index at which the
     * Strings begin to differ.</p>
     *
     * <p>For example,
     * <code>indexOfDifference(new String[] {"i am a machine", "i am a robot"}) -> 7</code></p>
     *
     * <pre>
     * indexOfDifference(null) = -1
     * indexOfDifference(new String[] {}) = -1
     * indexOfDifference(new String[] {"abc"}) = -1
     * indexOfDifference(new String[] {null, null}) = -1
     * indexOfDifference(new String[] {"", ""}) = -1
     * indexOfDifference(new String[] {"", null}) = 0
     * indexOfDifference(new String[] {"abc", null, null}) = 0
     * indexOfDifference(new String[] {null, null, "abc"}) = 0
     * indexOfDifference(new String[] {"", "abc"}) = 0
     * indexOfDifference(new String[] {"abc", ""}) = 0
     * indexOfDifference(new String[] {"abc", "abc"}) = -1
     * indexOfDifference(new String[] {"abc", "a"}) = 1
     * indexOfDifference(new String[] {"ab", "abxyz"}) = 2
     * indexOfDifference(new String[] {"abcde", "abxyz"}) = 2
     * indexOfDifference(new String[] {"abcde", "xyz"}) = 0
     * indexOfDifference(new String[] {"xyz", "abcde"}) = 0
     * indexOfDifference(new String[] {"i am a machine", "i am a robot"}) = 7
     * </pre>
     *
     * @param strs  array of strings, entries may be null
     * @return the index where the strings begin to differ; -1 if they are all equal
     * @since 2.4
     */
    public static int indexOfDifference(String[] strs) {
        if (strs == null || strs.length <= 1) {
            return -1;
        }
        boolean anyStringNull = false;
        boolean allStringsNull = true;
        int arrayLen = strs.length;
        int shortestStrLen = Integer.MAX_VALUE;
        int longestStrLen = 0;

        // find the min and max string lengths; this avoids checking to make
        // sure we are not exceeding the length of the string each time through
        // the bottom loop.
        for (int i = 0; i < arrayLen; i++) {
            if (strs[i] == null) {
                anyStringNull = true;
                shortestStrLen = 0;
            } else {
                allStringsNull = false;
                shortestStrLen = Math.min(strs[i].length(), shortestStrLen);
                longestStrLen = Math.max(strs[i].length(), longestStrLen);
            }
        }

        // handle lists containing all nulls or all empty strings
        if (allStringsNull || (longestStrLen == 0 && !anyStringNull)) {
            return -1;
        }

        // handle lists containing some nulls or some empty strings
        if (shortestStrLen == 0) {
            return 0;
        }

        // find the position with the first difference across all strings
        int firstDiff = -1;
        for (int stringPos = 0; stringPos < shortestStrLen; stringPos++) {
            char comparisonChar = strs[0].charAt(stringPos);
            for (int arrayPos = 1; arrayPos < arrayLen; arrayPos++) {
                if (strs[arrayPos].charAt(stringPos) != comparisonChar) {
                    firstDiff = stringPos;
                    break;
                }
            }
            if (firstDiff != -1) {
                break;
            }
        }

        if (firstDiff == -1 && shortestStrLen != longestStrLen) {
            // we compared all of the characters up to the length of the
            // shortest string and didn't find a match, but the string lengths
            // vary, so return the length of the shortest string.
            return shortestStrLen;
        }
        return firstDiff;
    }

    /**
     * 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();
    }
}

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