java--字符串拼接比较

/**
 * 字符串拼接
 */
public class StringAddDemo {
    public static void main(String[] args){
        testStringAdd();
        testConcat();
        testStringBuilder();
        testStringBuffer();
        //+:676
        //concat:243
        //StringBuilder:9
        //StringBuffer:1
    }
    public static void testStringAdd(){
        String s = "";
        long begin = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
            s = s + i;
        }
        long end = System.currentTimeMillis();
        System.out.println("+:" + (end-begin));
    }
    //连接
    public static void testConcat(){
        String s = "";
        long begin = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
            s = s.concat(String.valueOf(i));
        }
        long end = System.currentTimeMillis();
        System.out.println("concat:" + (end-begin));
    }
    //synchronization
    public static void testStringBuffer(){
        StringBuffer sb = new StringBuffer();
        long begin = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
            sb.append(i);
        }
        sb.toString();
        long end = System.currentTimeMillis();
        System.out.println("StringBuffer:" + (end-begin));
    }
    public static void testStringBuilder(){
        StringBuilder sb = new StringBuilder();
        long begin = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
            sb.append(i);
        }
        sb.toString();
        long end = System.currentTimeMillis();
        System.out.println("StringBuilder:" + (end-begin));
    }
}