在Java中,最快最有效的确定十进制值的方法是整数

试一试 Math.ceil :

private static boolean isInt(double x) {
     return x == Math.ceil(x);
}

编辑

private static boolean isInt1(double x) {
    return x == (int) x;
}

private static boolean isInt2(double x) {
    return x == Math.ceil(x);
}

private static boolean isInt3(double x) {
    return x % 1 == 0;
} 

isInt1 速度更快(在sunjre 1.6上)

double d = 123.456;
boolean dIsAnInteger = (d == (int)d);

0.9999999999999999 整数?可能不会。但请注意:

double val = 0;
for(int i=0;i<10;i++)
    System.out.println(val+=0.1);

这将打印出:

0.1
0.2
0.30000000000000004
0.4
0.5
0.6
0.7
0.7999999999999999
0.8999999999999999
0.9999999999999999

这是有问题的,因为在节目结束时 val 包含您认为应该是整数但不是整数的内容。

因此,通过集成类似于delta的 JUnit

private static boolean isInt(double x, double delta) {
    double ceil = Math.ceil(x);
    return x-delta<ceil && x+delta>ceil;
}

private static boolean isInt(double x) {
    return isInt(x, 0.000000001);
}

现在 isInt(val)