[Java] 반올림 올림 버림

1. 반올림

Math.round()

double pie=3.141592;
System.out.println(Math.round(pie)); 		 //3;
System.out.println(Math.round(pie*10)/10.0); 	 //3.1;
System.out.println(Math.round(pie*100)/100.0);	 //3.14;
System.out.println(Math.round(pie*1000)/1000.0); //3.142;

String.format()

double pie=3.141592;
System.out.println(String.format("%.0f", pie)); //3
System.out.println(String.format("%.1f", pie)); //3.1
System.out.println(String.format("%.2f" ,pie)); //3.14
System.out.println(String.format("%.3f" ,pie)); //3.142

 

2. 올림 ,버림

double pie=3.141592;
System.out.println(Math.ceil(pie)); 	 //4.0;
System.out.println(Math.floor(pie)); 	 //3.0;