Revise later
SpaceTo flip
If confident
All Flashcards
What does the following code output?
`Integer num = new Integer(10);
int val = num.intValue();
System.out.println(val);`
10
What does the following code output?
`Double num = new Double(3.14);
double val = num.doubleValue();
System.out.println(val);`
3.14
What does the following code output?
`Integer num = 5;
int val = num;
System.out.println(val);`
5
What does the following code output?
`Double num = 2.718;
double val = num;
System.out.println(val);`
2.718
What does the following code output?
`Integer num = null;
int val = 0;
try {
val = num;
} catch (NullPointerException e) {
System.out.println("NullPointerException caught!");
}
`
NullPointerException caught!
How are wrapper classes used in data validation?
Wrapper classes can be used to represent nullable values in databases, which can be useful when a field is not required.
How are wrapper classes used in generic data structures?
Generic data structures like `ArrayList<Integer>` require objects, so wrapper classes are used to store primitive data.
What is a wrapper class?
A class that encapsulates a primitive data type, allowing it to be treated as an object.
What is the Integer class?
A wrapper class for the primitive type `int`.
What is the Double class?
A wrapper class for the primitive type `double`.
What is autoboxing?
The automatic conversion of a primitive type to its corresponding wrapper class object.
What is unboxing?
The automatic conversion of a wrapper class object to its corresponding primitive type.