Question

Let’s first consider the following expressions in Java.

Integer temp = new Integer(1);
System.out.println(temp.equals(1));

if(temp.equals(1))
{
     System.out.println("The if block executed.");
}

These all statements work just fine. There is no question about it. The expression temp.equals(1) is evaluated to true as expected and the only statement within the if block is executed consequently.

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Now, when I change the data type from Integer to Long, the statement temp1.equals(1) is unexpectedly evaluated to false as follows.

Long temp1 = new Long(1);
System.out.println(temp1.equals(1));

if(temp1.equals(1))
{
    System.out.println("The if block executed.");
}

These are the equivalent statements to those mentioned in the preceding snippet just the data type has been changed and they behave exactly opposite.

The expression temp1.equals(1) is evaluated to false and consequently, the only statement within the if block is not executed which the reverse of the preceding statements. How?

Answer 1

You’re comparing a Long to an int. The javadoc for java.lang.Long#equals says that the equals method

Compares this object to the specified object. The result is true if and only if the argument is not null and is a Long object that contains the same long value as this object.

Instead try System.out.println(new Long(1).equals(1L)); Now that you’re comparing a Long to a Long instead of a Long to an Integer, it will print true.