Java Autoboxing - Primitive Type to Wrapper Object
In autoboxing, the Java compiler automatically converts primitive types into their corresponding wrapper class objects. For example,
int a = 56;
// autoboxing
Integer aObj = a;
Autoboxing has a great advantage while working with Java collections.
Example 1: Java Autoboxing
Output
ArrayList: [5, 6]
In the above example, we have created an array list of Integer type. Hence the array list can only hold objects of Integer type.
Notice the line,
list.add(5);
Here, we are passing primitive type value. However, due to autoboxing, the primitive value is automatically converted into an Integer object and stored in the array list.
Java Unboxing - Wrapper Objects to Primitive Types
In unboxing, the Java compiler automatically converts wrapper class objects into their corresponding primitive types. For example,
// autoboxing
Integer aObj = 56;
// unboxing
int a = aObj;
Like autoboxing, unboxing can also be used with Java collections.
Example 2: Java Unboxing
Output
ArrayList: [5, 6] Value at index 0: 5
In the above example, notice the line,
int a = list.get(0);
Here, the get() method returns the object at index 0. However, due to unboxing, the object is automatically converted into the primitive type int and assigned to the variable a.