On Java 7's equals() and deepEquals()

Question

Method description says:

Returns true if the arguments are deeply equal to each other and false otherwise... Equality is determined by using the equ

Answer 1

Attaching a very good example i found on javarevisited.blogspot.in

public class ArrayCompareTest {

public static void main(String args[]) {

   //comparing primitive int arrays in Java
    int[] i1 = new int[] {1,2,3,4};
    int[] i2 = new int[] {1,2,3,4};
    int[] i3 = new int[] {0,2,3,4};

    //Arrays.equals() compare Array and return true if both array are equal
    //i..e either both of them are null or they are identical in length, and each pair
    //match each other e.g. i[0]=i2[0], i[1]=i2[1] and so on

    //i1 and i2 should be equal as both contains same elements
    boolean result = Arrays.equals(i1, i2);
    System.out.println("Comparing int array i1: " + Arrays.toString(i1)
                        + " and i1: " + Arrays.toString(i2));
    System.out.println("Does array i1 and i2 are equal : " + result);

    //array ii2 and i3 are not equals as only length is same, first pair is not same
    result = Arrays.equals(i2, i3);
    System.out.println("Comparing int array i2: " + Arrays.toString(i2)
                        + " and i3: " + Arrays.toString(i3));
    System.out.println("Does array i2 and i3 are equal : " + result);

    //comparing floating point or double arrays in Java
    double[] d1 = new double[] {1.5, 2.4, 3.2, 4,1};
    double[] d2 = new double[] {1.5, 2.4, 3.2, 4,1};
    double[] d3 = new double[] {0.0, 2.4, 3.2, 4,1};

    //Comparing two floating-point arrays using Arrays.equals() in Java

    //double array d1 and d2 should be equal - length same, each index matches
    result = Arrays.equals(d1, d2);
    System.out.println("Comparing double array d1: " + Arrays.toString(d1)
                        + " and d2: " + Arrays.toString(d2));
    System.out.println("Does double array d1 and d2 are equal : " + result);

    //double array d2 and d3 is not equal - length same, first pair does not match
    result = Arrays.equals(d2, d3);
    System.out.println("Comparing double array d2: " + Arrays.toString(d2)
                        + " and d3: " + Arrays.toString(d3));
    System.out.println("Does double array d2 and d3 are same : " + result);

    //comparing Object array, here we will use String array
    String[] s1 = new String[]{"One", "Two", "Three"};
    String[] s2 = new String[]{"One", "Two", "Three"};
    String[] s3 = new String[]{"zero", "Two", "Three"};

    //String array s1 and s2 is equal - length same, each pair matches
    result = Arrays.equals(s1, s2);
    System.out.println("Comparing two String array s1: " + Arrays.toString(s1)
                        + " and s2: " + Arrays.toString(s2));

    System.out.println("Are both String array s1 and s2 are equal : " + result);

    //String array s2 and s3 is not equal - length same, first pair different
    result = Arrays.equals(d2, d3);
    System.out.println("Comparing two String array s2: " + Arrays.toString(s2)
                         + " and s3: " + Arrays.toString(s3));

    System.out.println("Are both String array s2 and s3 are equal : " + result);

    //Comparing nested arrays with equals and deepEquals method
    //Arrays.equals() method does not compare recursively,
    //while deepEquals() compare recursively
    //if any element inside Array is type of Array itself,
    //as here second element is String array

    Object[] o1 = new Object[]{"one", new String[]{"two"}};
    Object[] o2 = new Object[]{"one", new String[]{"two"}};

    System.out.println("Object array o1: " + Arrays.toString(o1) + " and o2: "
                        + Arrays.toString(o2));
    System.out.println("Comparing Object Array o1 and o2 with Arrays.equals : "
                        + Arrays.equals(o1, o2));
    System.out.println("Comparing Object Array o1 and o2 with Arrays.deepEquals : "
                        + Arrays.deepEquals(o1, o2));
} 

}

Output: Comparing int array i1: [1, 2, 3, 4] and i1: [1, 2, 3, 4] Does array i1 and i2 are equal : true

Comparing int array i2: [1, 2, 3, 4] and i3: [0, 2, 3, 4] Does array i2 and i3 are equal : false

Comparing double array d1: [1.5, 2.4, 3.2, 4.0, 1.0] and d2: [1.5, 2.4, 3.2, 4.0, 1.0] Does double array d1 and d2 are equal : true

Comparing double array d2: [1.5, 2.4, 3.2, 4.0, 1.0] and d3: [0.0, 2.4, 3.2, 4.0, 1.0] Does double array d2 and d3 are same : false

Comparing two String array s1: [One, Two, Three] and s2: [One, Two, Three] Are both String array s1 and s2 are equal : true

Comparing two String array s2: [One, Two, Three] and s3: [zero, Two, Three] Are both String array s2 and s3 are equal : false

Object array o1: [one, [Ljava.lang.String;@19821f] and o2: [one, [Ljava.lang.String;@addbf1] Comparing Object Array o1 and o2 with Arrays.equals : false Comparing Object Array o1 and o2 with Arrays.deepEquals : true