250+ TOP MCQs on Java.lang – Double & Float Wrappers and Answers [2024]

This set of Java Multiple Choice Questions & Answers (MCQs) on “Double & Float Wrappers”.

1. Which of these is a super class of wrappers Double and Float?
a) Long
b) Digits
c) Float
d) Number

Answer: d
Clarification: Number is an abstract class containing subclasses Double, Float, Byte, Short, Integer and Long.

2. Which of the following methods return the value as a double?
a) doubleValue()
b) converDouble()
c) getDouble()
d) getDoubleValue()

Answer: a
Clarification: None.

3. Which of these methods can be used to check whether the given value is a number or not?
a) isNaN()
b) isNumber()
c) checkNaN()
d) checkNumber()

Answer: a
Clarification: isNaN() methods returns true if num specified is not a number, otherwise it returns false.

4. Which of these method of Double wrapper can be used to check whether a given value is infinite or not?
a) Infinite()
b) isInfinite()
c) checkInfinite()
d) None of the mentioned

Answer: b
Clarification: isInfinite() methods returns true if the specified value is an infinite value otherwise it returns false.

5. Which of these exceptions is thrown by compareTo() method defined in a double wrapper?
a) IOException
b) SystemException
c) CastException
d) ClassCastException

Answer: d
Clarification: compareTo() methods compare the specified object to be double, if it is not then ClassCastException is thrown.

6. What will be the output of the following Java code?

```
    class Output 
```
```
    {
```

        public static void main(String args[])

```
        {
```

            Double i = new Double(257.5);

```
            boolean x = i.isNaN();
```
```
            System.out.print(x);
```
```
        }
```
```
    }
```

a) true
b) false
c) 0
d) 1

Answer: b
Clarification: i.isNaN() method returns returns true if i is not a number and false when i is a number. Here false is returned because i is a number i:e 257.5.
Output:

$ javac Output.java
$ java Output
false

7. What will be the output of the following Java code?

```
    class Output
```
```
    {
```

        public static void main(String args[])

```
        {
```

            Double i = new Double(257.578);

```
            int x = i.intValue();
```
```
            System.out.print(x);
```
```
        }
```
```
    }
```

a) 0
b) 1
c) 256
d) 257

Answer: d
Clarification: i.intValue() method returns the value of wrapper i as a Integer. i is 257.578 is double number when converted to an integer data type its value is 257.
Output:

$ javac Output.java
$ java Output
257

8. What will be the output of the following Java code?

```
    class Output
```
```
    {
```

        public static void main(String args[])

```
        {
```

	    Double i = new Double(257.578123456789);

```
            float x = i.floatValue();
```
```
            System.out.print(x);
```
```
        }
```
```
    }
```

a) 0
b) 257.0
c) 257.57812
d) 257.578123456789

Answer: c
Clarification: floatValue() converts the value of wrapper i into float, since float can measure till 5 places after decimal hence 257.57812 is stored in floating point variable x.
Output:

$ javac Output.java
$ java Output
257.57812

9. What will be the output of the following Java code?

```
    class Output
```
```
    {
```

        public static void main(String args[])

```
        {
```

            Double y = new Double(257.57812);

	    Double i = new Double(257.578123456789);

```
            try
```
```
            {
```
```
	        int x = i.compareTo(y);
```
```
                System.out.print(x);
```
```
            }
```
```
            catch(ClassCastException e)
```
```
            {
```

                System.out.print("Exception");

```
            }
```
```
	}
```
```
    }
```

a) 0
b) 1
c) Exception
d) None of the mentioned

Answer: b
Clarification: i.compareTo() methods two double values, if they are equal then 0 is returned and if not equal then 1 is returned, here 257.57812 and 257.578123456789 are not equal hence 1 is returned and stored in x.
Output:

$ javac Output.java
$ java Output
1

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