OnJava8-Examples/references/MutableInteger.java

// references/MutableInteger.java
// <20>2015 MindView LLC: see Copyright.txt
// A changeable wrapper class.
import java.util.*;

class IntValue {
  private int n;
  public IntValue(int x) { n = x; }
  public int getValue() { return n; }
  public void setValue(int n) { this.n = n; }
  public void increment() { n++; }
  @Override
  public String toString() {
    return Integer.toString(n);
  }
}

public class MutableInteger {
  public static void main(String[] args) {
    List<IntValue> v = new ArrayList<>();
    for(int i = 0; i < 10; i++)
      v.add(new IntValue(i));
    System.out.println(v);
    for(int i = 0; i < v.size(); i++)
      v.get(i).increment();
    System.out.println(v);
  }
}
/* Output:
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
*/