Java中Math.round(-1.5)等于多少

Math.round(-1.5)的返回值是-1。四舍五入的原理是在参数上加0.5然后做向下取整。
我们可以通过大量实验看下结果

public class test {
	public static void main(String[] args){
		System.out.println(Math.round(1.3));   //1
		System.out.println(Math.round(1.4));   //1
		System.out.println(Math.round(1.5));   //2
		System.out.println(Math.round(1.6));   //2
		System.out.println(Math.round(1.7));   //2
		System.out.println(Math.round(-1.3));  //-1
		System.out.println(Math.round(-1.4));  //-1
		System.out.println(Math.round(-1.5));  //-1
		System.out.println(Math.round(-1.6));  //-2
		System.out.println(Math.round(-1.7));  //-2
	}
}