String、StringBuffer、StringBuilder效率测试

/**
 * @auto dh
 * @create 2020-03-25-15:16
 */
public class StringTest {
    public static void main(String[] args) {
        long startTime = 0L;
        long endTime = 0L;
        String text = "";
        StringBuffer sf = new StringBuffer("");
        StringBuilder sl = new StringBuilder("");

        /*StringBuffer效率测试*/
        System.out.println("StringBuffer效率测试");
        startTime = System.currentTimeMillis();
        for (int i = 0; i < 20000; i++) {
            sf.append(String.valueOf(i));
        }
        endTime = System.currentTimeMillis();
        System.out.println(endTime - startTime);
        /*StringBuilder效率测试*/
        System.out.println("StringBuilder效率测试");
        startTime=System.currentTimeMillis();
        for(int i=0;i<20000;i++){
            sl.append(String.valueOf(i));
        }
        endTime=System.currentTimeMillis();
        System.out.println(endTime-startTime);
        /*String效率测试*/
        System.out.println("String效率测试");
        startTime=System.currentTimeMillis();
        for(int i=0;i<20000;i++){
            text+=i;
        }
        endTime=System.currentTimeMillis();
        System.out.println(endTime-startTime);
    }
}