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DoubleEquivalence.java
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68 lines (56 loc) · 1.97 KB
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// 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) { //比较0和最小的浮点数 test(0, Double.MIN_VALUE); System.out.println("------------------------"); //最大值 和 （最大值 和 （最小值只差的一百万倍））比较 一个非常大的数值减去一个相对较小的数值, //非常大的数值并不会发生显著变化。这个叫做 <b> 舍入误差 <\b> test(Double.MAX_VALUE, Double.MAX_VALUE - Double.MIN_VALUE * 1_000_000); System.out.println("------------------------"); test(2.1, 3.5); System.out.println("------------------------"); System.out.println(Double.MIN_VALUE); //2^-1074 System.out.println(Double.MAX_VALUE); }}/* Output:0.000000e+00==4.900000e-324 falseAutomatic:0.000000e+00==4.900000e-324 false falsenew Double():0.000000e+00==4.900000e-324 false falseDouble.valueOf():0.000000e+00==4.900000e-324 false false------------------------1.797693e+308==1.797693e+308 trueAutomatic:1.797693e+308==1.797693e+308 false truenew Double():1.797693e+308==1.797693e+308 false trueDouble.valueOf():1.797693e+308==1.797693e+308 false true*/