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Mutable and immutable

Table of contents

  1. Mutable and immutable
  2. The final keyword
  3. When should I use the final keyword?

Mutable and immutable

Example

package demo;

public class App {

  public static void main( String[] args ) {
    /* Mutable */
    int a = 2;
    a++;

    /* Immutable */
    final int b = 3;

    /* Immutable (initialised after declared) */
    final int c;
    c = 3;

    System.out.printf( "a = %d%n", a );
    System.out.printf( "b = %d%n", b );
    System.out.printf( "c = %d%n", c );
  }
}

Output

a = 3
b = 3
c = 3

The final keyword

The final keyword marks a variable as immutable. This means that the variable’s value, be it the primitive value itself or the reference, cannot be changed. This means that the Java stack value, and not the Java heap value, cannot be modified.

The final keyword affects the Java stack and not the Java heap contents.

When should I use the final keyword?

🚧 Pending 🚧