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The Java Interview Handbook: 300+ Interview Questions

Boxing

Explore the concept of boxing in Java, focusing on how object wrappers cache primitive values within certain ranges. Understand why using the == operator on boxed values may yield true or false depending on caching. This lesson helps clarify the behavior of Integer and other wrapper classes, enhancing your grasp of Java's memory optimization and equality comparisons.

We'll cover the following...
1.

What is boxing or autoboxing?

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Technical Quiz
1.

What will be the output of the following code snippet?

        Long value = 7L;
        System.out.println(value.equals(7));
A.

True

B.

False

1 / 1
Technical Quiz
1.

What will be the output of the following snippet?

        Long value1 = 7L;
        System.out.println(value1 == 7);
A.

true

B.

false

1 / 1
Technical Quiz
1.

What will be the output of the following change made to the snippet presented earlier?

        Long value = 7L;
        System.out.println(value.equals(7L));
A.

true

B.

false

1 / 1
Technical Quiz
1.

What will be the output of the following snippet?

        Long value1 = 7L;
        Long value2 = 7L;
        System.out.println(value1 == value2);
A.

true

B.

false

1 / 1
Technical Quiz
1.

What will be the output of the following snippet?

        Long value1 = 7L;
        Long value2 = 7L;
        System.out.println(value1.equals(value2));
A.

true

B.

false

1 / 1
Technical Quiz
1.

What will be the output of the following snippet?

        Long value1 = 20007L;
        System.out.println(value1 == 20007L);
A.

true

B.

false

1 / 1
Technical Quiz
1.

What will be the output of the following snippet?

        Long value1 = 20007L;
        Long value2 = 20007L;
        System.out.println(value1 == value2);
A.

true

B.

false

1 / 1

Questions 4 - 8 are below:

Java
class Demonstration {
    public static void main( String args[] ) {
        Long value = 7L;
        System.out.println("\nLong value = 7L;\nvalue.equals(7) " + value.equals(7));
        System.out.println("value == 7 " + (value == 7));
        System.out.println("value.equals(7L) " + value.equals(7L));
        Long value1 = 7L;
        Long value2 = 7L;
        System.out.println("\n\nLong value1 = 7L;\nLong value2 = 7L;\nvalue1 == value2 " + (value1 == value2));
        System.out.println("value1.equals(value2) " + value1.equals(value2));
        value1 = 20007L;
        value2 = 20007L;
        System.out.println("\n\nvalue1 = 20007L;\nvalue2 = 20007L;\nvalue1 == 20007L " + (value1 == 20007L));
        System.out.println("value1 == value2 " + (value1 == value2));
        System.out.println("value1.equals(20007L) " + value1.equals(20007L));
    }
}

Note in the above snippet how the comparison using == operator for the variables initialized to 7 yields true, whereas the same comparison when values are initialized ...