OnJava8-Examples/operators/Equivalence.java

// operators/Equivalence.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.

public class Equivalence {
  static void show(String desc, Integer n1, Integer n2) {
    System.out.println(desc + ":");
    System.out.printf(
      "%d==%d %b %b%n", n1, n2, n1 == n2, n1.equals(n2));
  }
  @SuppressWarnings("deprecation")
  public static void test(int value) {
    Integer i1 = value;                             // [1]
    Integer i2 = value;
    show("Automatic", i1, i2);
    // Old way, deprecated since Java 9:
    Integer r1 = new Integer(value);                // [2]
    Integer r2 = new Integer(value);
    show("new Integer()", r1, r2);
    // Preferred since Java 9:
    Integer v1 = Integer.valueOf(value);            // [3]
    Integer v2 = Integer.valueOf(value);
    show("Integer.valueOf()", v1, v2);
    // Primitives can't use equals():
    int x = value;                                  // [4]
    int y = value;
    // x.equals(y); // Doesn't compile
    System.out.println("Primitive int:");
    System.out.printf("%d==%d %b%n", x, y, x == y);
  }
  public static void main(String[] args) {
    test(127);
    test(128);
  }
}
/* Output:
Automatic:
127==127 true true
new Integer():
127==127 false true
Integer.valueOf():
127==127 true true
Primitive int:
127==127 true
Automatic:
128==128 false true
new Integer():
128==128 false true
Integer.valueOf():
128==128 false true
Primitive int:
128==128 true
*/