Three methods of the Java Math class ceil floor round usage

ceil, floor, round Usage of Math Class

ceil () method

It means rounding up, and the result of Math. ceil (12.3) is 13, and the result of Math. ceil (-12.7) is-12;

floor () method

It means rounding down, and the result of Math. floor (12.7) is 12, and the result of Math. floor (-12.3) is-13;

round () method

It means "4 round 5 in", the result of Math. round (12.3) is 12, and the result of Math. round (-12.7) is-13;

Summary of floor, round and ceil for Math

floor returns the largest integer not greater than

round is the calculation of 4 rounded by 5 integers, and the integer is greater than it when entering

round method, which means "4 rounding 5 inputs", the algorithm is Math. floor (x+0.5), that is, adding 0.5 to the original number and rounding it down, so the result of Math. round (11.5) is 12, and the result of Math. round (-11.5) is-11.

ceil is the smallest integer not less than it

Look at examples

	Math.floor	Math.round	Math.ceil
1.4	1	1	2
1.5	1	2	2
1.6	1	2	2
-1.4	-2	-1	-1
-1.5	-2	-1	-1
-1.6	-2	-2	-1

The test procedure is as follows:

 
public class MyTest {   
  public static void main(String[] args) {   
    double[] nums = { 1.4, 1.5, 1.6, -1.4, -1.5, -1.6 };   
    for (double num : nums) {   
      test(num);   
    }   
  }   
private static void test(double num) {   
    System.out.println("Math.floor(" + num + ")=" + Math.floor(num));   
    System.out.println("Math.round(" + num + ")=" + Math.round(num));   
    System.out.println("Math.ceil(" + num + ")=" + Math.ceil(num));   
  }   
}  
 

Running result

Math.floor(1.4)=1.0
Math.round(1.4)=1
Math.ceil(1.4)=2.0
Math.floor(1.5)=1.0
Math.round(1.5)=2
Math.ceil(1.5)=2.0
Math.floor(1.6)=1.0
Math.round(1.6)=2
Math.ceil(1.6)=2.0
Math.floor(-1.4)=-2.0
Math.round(-1.4)=-1
Math.ceil(-1.4)=-1.0
Math.floor(-1.5)=-2.0
Math.round(-1.5)=-1
Math.ceil(-1.5)=-1.0
Math.floor(-1.6)=-2.0
Math.round(-1.6)=-2
Math.ceil(-1.6)=-1.0