string 与 stringbuffer的性能比较

static void testString(){

   String sf = "abcdefghijklmnopqrstuvwxyz";
   int tick = 10000;
   long startTime = System.currentTimeMillis();
   String str1 ="";
   
   for (int i = 0; i < tick;i++){
    str1 += sf;
   }

   long endTime = System.currentTimeMillis();

System.out.println("string:" + (endTime - startTime) + "ms");
}

static void testStringBuffer(){
StringBuffer sfbBuffer = new StringBuffer("abcdefghijklmnopqrstuvwxyz");
int tick = 10000;
long startTime = System.currentTimeMillis();
StringBuffer str1 = new StringBuffer();
for (int i = 0; i < tick;i++){
    str1.append(sfbBuffer);
   }
   long endTime = System.currentTimeMillis();

   System.out.println("stringBuffer:" + (endTime - startTime) + "ms");
}

运行二次结果

string:3042ms

stringBuffer:5ms

string:3238ms

stringBuffer:5ms

当操作量大的时候stringBuffer的性能优势就显示出来了