Java double类型不一定满足加法交换律与结合律

代码

    private static void testAddition() {
        double a = 2.525;
        double b = 2.085714285714286;
        double c = 1.8142857142857143;

        System.out.println("测试交换律：");
        double abc = a + b + c;
        double acb = a + c + b;
        System.out.println("a + b + c: " + abc);
        System.out.println("a + c + b: " + acb);

        System.out.println("测试结合律：");
        double ABc = (a + b) + c;
        double aBC = a + (b + c);
        System.out.println("(a + b) + c: " + ABc);
        System.out.println("a + (b + c): " + aBC);

        System.out.println("其他：");
        double bc = b + c;
        double cb = c + b;
        System.out.println("b + c: " + bc);
        System.out.println("c + b: " + cb);
        double a_bc = a + (b + c);
        double a_cb = a + (c + b);
        System.out.println("a + (b + c): " + a_bc);
        System.out.println("a + (c + b): " + a_cb);
    }

运行结果

可以看出，由于double类型的精度损失，带来了微小误差，如果使用四舍六入五成双算法保留两位小数，6.425 约为 6.42，6.425000000000001 约为 6.43