[Java] 29. Test4 풀이 (결과가 나오도록 함수 구현하기)

package chap11;
/*
 * 결과가 나오도록  함수 구현하기
 * double round(실수형,소숫점이하 자리수)
 * double truncate(실수형,소숫점이하 자리수)
 */
public class Test0321_4 {
	public static void main(String[] args) {
		System.out.println(round(3.1215,1)); //3.1
		System.out.println(round(3.1215,2)); //3.12
		System.out.println(round(3.1215,3)); //3.122
		System.out.println(round(3.1215,4)); //3.1215
		System.out.println(truncate(3.15345,1));  //3.1
		System.out.println(truncate(3.15345,2));  //3.15
		System.out.println(truncate(3.15345,3));  //3.153
		System.out.println(truncate(3.15345,4));  //3.1534
	}
	static double round(double d, int i) {
		String sf = String.format("%."+i+"f", d);
		return Double.parseDouble(sf);
	}
	static double truncate(double d, int i) {
		int num10 =1;
		for(int a=0; a < i;a++) {
			num10 *= 10;
		}
		return (int)(d * num10)/(double)num10;
	}	
}