Objects that cannot be modified are immune to aliasing

 

// : appendixa:Immutable1.java
// Objects that cannot be modified are immune to aliasing.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.

public class Immutable1 {

  private int data;

  public Immutable1(int initVal) {
    data = initVal;
  }

  public int read() {
    return data;
  }

  public boolean nonzero() {
    return data != 0;
  }

  public Immutable1 multiply(int multiplier) {
    return new Immutable1(data * multiplier);
  }

  public static void f(Immutable1 i1) {
    Immutable1 quad = i1.multiply(4);
    System.out.println("i1 = " + i1.read());
    System.out.println("quad = " + quad.read());
  }

  public static void main(String[] args) {
    Immutable1 x = new Immutable1(47);
    System.out.println("x = " + x.read());
    f(x);
    System.out.println("x = " + x.read());

  }
} ///:~

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