Autoboxing and Unboxing in Java

Autoboxing is the automatic conversion that the Java compiler makes between the primitive types and their corresponding object wrapper classes. If the conversion goes the other way, this is called unboxing

Autoboxing

Character ch = 'a';

List<Integer> li = new ArrayList<>();

for (int i = 1; i < 50; i += 2)

    li.add(i); //it creates an Integer object from i and adds the object to li.

 ******************

List<Integer> li = new ArrayList<>();

for (int i = 1; i < 50; i += 2)

    li.add(Integer.valueOf(i)); // compiler converts the previous code to the following at runtime

unboxing

Integer i = new Integer(-8);

        // Unboxing through method invocation

        int absVal = absoluteValue(i);

List<Double> ld = new ArrayList<>();

        ld.add(3.1416);    // autoboxed through method invocation.

        // Unboxing through assignment

        double pi = ld.get(0);

Primitive type	Wrapper class
boolean	Boolean
byte	Byte
char	Character
float	Float
int	Integer
long	Long
short	Short
double	Double

Benefits of Autoboxing / Unboxing

• Autoboxing / Unboxing lets us use primitive types and Wrapper class objects interchangeably.
• We don't have to perform explicit typecasting
• It helps prevent errors, but may lead to unexpected results sometimes. Hence must be used with care.