数字处理

1.double 的向上，向下，四舍五入，以及转为 int

1.向输出上取整

public static void mathCeil() {
    Double number = 5.3;
    // Double 向上取整
    double ceil = Math.ceil(number);
    System.out.println("number:" + number);
    System.out.println("ceil:" + ceil);
    int ceilRes = new Double(ceil).intValue();
    System.out.println("ceilRes:" + ceilRes);
}

输出：

number:5.3
ceil:6.0
ceilRes:6

2.向下取整

public static void mathFloor () {
    Double number = 5.9;
    // Double 向下取整
    double floor = Math.floor(number);
    System.out.println("number:" + number);
    System.out.println("floor:" + floor);
    int floorRes = new Double(floor).intValue();
    System.out.println("floorRes:" + floorRes);
}

输出：

number:5.9
floor:5.0
floorRes:5

3.四舍五入

public static void mathRound() {
    Double number1 = 5.9;
    Double number2 = 5.3;
    // Double number1 四舍五入
    double round1 = Math.round(number1);
    System.out.println("number1:" + number1);
    System.out.println("round1:" + round1);
    int round1Res = new Double(round1).intValue();
    System.out.println("round1Res:" + round1Res);
    // Double number2 四舍五入
    double round2 = Math.round(number2);
    System.out.println("number1:" + number2);
    System.out.println("round2:" + round2);
    int round2Res = new Double(round2).intValue();
    System.out.println("round2Res:" + round2Res);
}

输出：

number1:5.9
round1:6.0
round1Res:6

number1:5.3
round2:5.0
round2Res:5