Autoboxing in Java is the automatic transformation of primitive data types ((int, float, double) into their corresponding Wrapper class object (Integer, Float, Double) by Java compiler.
One must also know about Unboxing, which means he automatic transformation of wrapper class object into their corresponding primitive data types.
Autoboxing or automatic transformation of primitive data types into Wrapper class by Java compiler takes place when:
- a primitive data type is passed in a parameter of method, which is expecting an object of corresponding wrapper class
- a primitive data type is assigned to a variable of the corresponding wrapper class.
| Primitive data type | Wrapper class |
|---|---|
| boolean | Boolean |
| int | Integer |
| char | Character |
| float | Float |
| double | Double |
| byte | Byte |
| long | Long |
| short | Short |
Following is the example of Autoboxing in Java:
public class MainClass {
public static void main(String args[]) {
Boolean booleanObject = true;
if (booleanObject){
System.out.println("a is true");
}
Integer i = 'x'; // box a int
int i2 = i; // unbox a int
System.out.println("i2 is " + i2);
}
}
Output:
a is true
i2 is x