OnJava8-Examples/operators/DoubleEquivalence.java

// operators/DoubleEquivalence.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 DoubleEquivalence {
  static void show(String desc, Double n1, Double n2) {
    System.out.println(desc + ":");
    System.out.printf(
      "%e==%e %b %b%n", n1, n2, n1 == n2, n1.equals(n2));
  }
  @SuppressWarnings("deprecation")
  public static void test(double x1, double x2) {
    // x1.equals(x2) // Won't compile
    System.out.printf("%e==%e %b%n", x1, x2, x1 == x2);
    Double d1 = x1;
    Double d2 = x2;
    show("Automatic", d1, d2);
    Double r1 = new Double(x1);
    Double r2 = new Double(x2);
    show("new Double()", r1, r2);
    Double v1 = Double.valueOf(x1);
    Double v2 = Double.valueOf(x2);
    show("Double.valueOf()", v1, v2);
  }
  public static void main(String[] args) {
    test(0, Double.MIN_VALUE);
    System.out.println("------------------------");
    test(Double.MAX_VALUE,
      Double.MAX_VALUE - Double.MIN_VALUE * 1_000_000);
  }
}
/* Output:
0.000000e+00==4.900000e-324 false
Automatic:
0.000000e+00==4.900000e-324 false false
new Double():
0.000000e+00==4.900000e-324 false false
Double.valueOf():
0.000000e+00==4.900000e-324 false false
------------------------
1.797693e+308==1.797693e+308 true
Automatic:
1.797693e+308==1.797693e+308 false true
new Double():
1.797693e+308==1.797693e+308 false true
Double.valueOf():
1.797693e+308==1.797693e+308 false true
*/