Mega Code Archive
Concatenate Java arrays
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/*
* Convenience methods for working with Java arrays.
* Copyright (C) 2005 Stephen Ostermiller
* http://ostermiller.org/contact.pl?regarding=Java+Utilities
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 for more details.
*
* See COPYING.TXT for details.
*/
import java.io.IOException;
import java.lang.reflect.Array;
/**
* Convenience methods for working with Java arrays.
* More information about this class is available from <a target="_top" href=
* "http://ostermiller.org/utils/ArrayHelper.html">ostermiller.org</a>.
*
* @author Stephen Ostermiller http://ostermiller.org/contact.pl?regarding=Java+Utilities
* @since ostermillerutils 1.06.00
*/
public final class ArrayHelper {
/**
* Concatenates the given arrays into a single long array.
* The returned array will be of the common super type of the
* two given arrays.
* <p>
* For example it can be called like this:<br>
* <pre>
* String[] arr = (String[])ArrayHelper.cat(new String[]{"one","two"}, new String[]{"three","four"});
* </pre>
*
* @param arr1 first array
* @param arr2 second array
* @return an array whose length is the sum of the given array's lengths and contains all the elements in the given arrays.
* @since ostermillerutils 1.06.00
*/
public static Object[] cat(Object[] arr1, Object[] arr2){
// Use reflection to find the super class of both arrays
Class<?> commonSuperClass = Object.class;
boolean foundcommonSuperClass=false;
for (Class<?> c1 = arr1.getClass().getComponentType(); !foundcommonSuperClass && !c1.equals(Object.class); c1 = c1.getSuperclass()){
for (Class<?> c2 = arr2.getClass().getComponentType(); !foundcommonSuperClass && !c2.equals(Object.class); c2 = c2.getSuperclass()){
if (c2.equals(c1)){
foundcommonSuperClass = true;
commonSuperClass = c1;
}
}
}
// Create a new array of the correct type
Object[] result = (Object[])Array.newInstance(commonSuperClass, arr1.length + arr2.length);
// Copy the two arrays into the large array
System.arraycopy(arr1, 0, result, 0, arr1.length);
System.arraycopy(arr2, 0, result, arr1.length, arr2.length);
return result;
}
/**
* Tests two arrays to see if the arrays are equal.
* Two arrays will be equal only if they are the same length
* and contain objects that are equal in the same order.
*
* @param arr1 first array
* @param arr2 second array
* @return true iff two arguments are equal
* @since ostermillerutils 1.06.00
*/
public static boolean equal(Object[] arr1, Object[] arr2){
if (arr1 == null && arr2 == null) return true;
if (arr1 == null || arr2 == null) return false;
if (arr1.length != arr2.length) return false;
for (int i=0; i<arr1.length; i++){
if (!equalObjects(arr1[i], arr2[i])) return false;
}
return true;
}
/**
* Tests if the two objects are equal
*
* @param o1 first object
* @param o2 second object
* @since ostermillerutils 1.06.00
*/
private static boolean equalObjects(Object o1, Object o2){
if (o1 == null && o2 == null) return true;
if (o1 == null || o2 == null) return false;
return o1.equals(o2);
}
}
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