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 equals method of the first argument.

Which (to me) suggests that Objects are deeply equal if every object they maintain references to are also equal using the equals() method. And every objects they have a reference to are also equal. And ..

So .. equality is determined by using the equals method of the first argument.

How is this different from .equals()? Assuming that we describe equals appropriately where, objects is equal to another object is every field of the object is equal to it as well.

Can you please provide an example illustrating the difference between Objects.deepEquals() and Objects.equals()?

Answer 1

String[] firstArray  = {"a", "b", "c"};
String[] secondArray = {"a", "b", "c"};

System.out.println("Are they equal 1    ? " + firstArray.equals(secondArray) );
System.out.println("Are they equal 2    ? " + Objects.equals(firstArray, secondArray) );

System.out.println("Are they deepEqual 1? " + Arrays.deepEquals(firstArray, secondArray) );
System.out.println("Are they deepEqual 2? " + Objects.deepEquals(firstArray, secondArray) );

will return

Are they equal 1    ? false
Are they equal 2    ? false
Are they deepEqual 1? true
Are they deepEqual 2? true

How come the "shallow" equals methods return false? This is because in Java, for arrays, equality is determined by object identity. In this example, firstArray and secondArray are distinct objects.

Doing String[] secondArray = firstArray instead will therefore return true for all four tests.