java–CharAt,StartWith

public class CharAtStartWithDemo {
    public static void main(String[] args){
        //jdk8
        testCharAt();//1
        testStartWith();//4
    }
    public static void testCharAt(){
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < 1000; i++) {
            sb.append(i);
            if (i < 999){
                sb.append(",");
            }
        }
        String s = sb.toString();
        int length = s.length();
        long begin = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
            if (s.charAt(0)=='a'&&s.charAt(1)=='b'&&s.charAt(2)=='c'){}
            if (s.charAt(length-1)=='a'&&s.charAt(length-2)=='b'&&s.charAt(length-3)=='c'){}
        }
        long end = System.currentTimeMillis();
        System.out.println(end-begin);
    }
    public static void testStartWith(){
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < 1000; i++) {
            sb.append(i);
            if (i < 999){
                sb.append(",");
            }
        }
        String s = sb.toString();
        int length = s.length();
        long begin = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
            if (s.startsWith("abc")){}
            if (s.endsWith("abc")){}
        }
        long end = System.currentTimeMillis();
        System.out.println(end-begin);
    }
}