A changeable wrapper class

 
// : appendixa:MutableInteger.java
// A changeable wrapper class.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.

import java.util.ArrayList;
import java.util.List;

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++;
  }

  public String toString() {
    return Integer.toString(n);
  }
}

public class MutableInteger {

  public static void main(String[] args) {
    List 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++)
      ((IntValue) v.get(i)).increment();
    System.out.println(v);

  }
} ///:~

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