Common wrapper methods in Java - Practice Problems & Coding Challenges

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Challenge - 5 Problems

💻 code output

intermediate

Output of Integer wrapper method usage

What is the output of the following Java code snippet using Integer wrapper methods?

Java

public class Main {
    public static void main(String[] args) {
        Integer num = Integer.valueOf("123");
        int result = num.intValue() + Integer.parseInt("77");
        System.out.println(result);
    }
}

A Compilation error

B 100

C 200

D 12377

💻 code output

intermediate

Output of Double wrapper method usage

What will be printed by this Java code using Double wrapper methods?

Java

public class Main {
    public static void main(String[] args) {
        Double d1 = Double.valueOf("10.5");
        double d2 = Double.parseDouble("2.5");
        System.out.println(d1.doubleValue() * d2);
    }
}

A 26.25

B 105.0

C 13.0

D Runtime error

💻 code output

advanced

Output of Boolean wrapper method usage

What is the output of this Java code snippet using Boolean wrapper methods?

Java

public class Main {
    public static void main(String[] args) {
        Boolean b1 = Boolean.valueOf("true");
        Boolean b2 = Boolean.valueOf("False");
        System.out.println(b1 && b2);
    }
}

A false

B Runtime exception

C Compilation error

D true

💻 code output

advanced

Output of Character wrapper method usage

What will this Java code print when using Character wrapper methods?

Java

public class Main {
    public static void main(String[] args) {
        Character ch = Character.valueOf('a');
        System.out.println(Character.toUpperCase(ch));
    }
}

A Compilation error

B a

C Runtime exception

D A

💻 code output

expert

Output of complex wrapper method chaining

What is the output of this Java code using multiple wrapper methods?

Java

public class Main {
    public static void main(String[] args) {
        String s = "256";
        Integer i = Integer.valueOf(s);
        Double d = Double.valueOf(i.doubleValue() / 4);
        System.out.println(d.intValue() + ":" + d);
    }
}

A 64:64

B 64:64.0

C 64.0:64.0

D Compilation error