Java Collection Equal equalsUnorderedCollections(Collection a, Collection b)

Description

Compares the elements of two collections using Object.equals on the elements.

License

Open Source License

Parameter

Parameter	Description
a	a parameter
b	a parameter

Return

True if a and b have the same number of elements and the elements are all equal.

Declaration

public static <T> boolean equalsUnorderedCollections(Collection<T> a, Collection<T> b) 

Method Source Code

//package com.java2s;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

public class Main {
    /**// w w  w .j av  a 2  s .c om
     * Compares the elements of two collections using Object.equals on the elements.  
     * Differences in the element order are not considered.
     * @param a
     * @param b
     * @return True if a and b have the same number of elements and the elements
     *         are all equal.
     */
    public static <T> boolean equalsUnorderedCollections(Collection<T> a, Collection<T> b) {

        // Do a quick check to see if a and b are the same object
        if (a == b) {
            return true;
        }

        // Ensure that both lists are the same size
        if (a.size() != b.size())
            return false;

        // Compare each element in turn and return false if any of them are different.
        List<T> _b = new ArrayList<T>(b);

        for (final T elemA : a) {

            boolean foundMatching = false;

            for (Iterator<T> iterB = _b.iterator(); iterB.hasNext();) {
                T elemB = iterB.next();
                if (equals(elemA, elemB)) {
                    iterB.remove();
                    foundMatching = true;
                    break;
                }
            }

            // We have walked past the end of the second list and still
            // cannot find a matching item.
            if (!foundMatching) {
                return false;
            }
        }

        // No mismatches were found, the list elements are equals
        return _b.isEmpty();
    }

    /**
     * Minor helper method that checks if 2 objects are either both null or equal using the equals()
     * method.  This makes long if statements (such as those found in equals() methods) easier to read. 
     * @param a
     * @param b
     * @return True if both a and b are null or if a.equals(b).  Otherwise false is returned.
     */
    public static boolean equals(Object a, Object b) {
        return (a == null ? b == null : a.equals(b));
    }
}

Related

1. equalsOne(final T o1, final Collection others)
2. equalsSet(Collection c1, Collection c2)
3. equalsSet(Collection c1, Collection c2)
4. equalsUnordered(Collection collection1, Collection collection2)
5. equalsUnordered(Collection collection1, Collection collection2)
6. equalTestData(Collection receivedDataSet)
7. getContainedEquals(Collection a, T b)
8. indexOfEquals(Collection collection, T element)
9. isCollectionEqual(Collection c1, Collection c2)