Java 中 String、StringBuffer、StringBuilder 的区别

String s = "";
for (int i = 0; i < 100000; i++) {
    s += 'a';  // 每次循环都创建新对象，性能极差
}

StringBuilder sb = new StringBuilder();
for (int i = 0; i < 100000; i++) {
    sb.append('a');  // 直接修改内部数组
}

StringBuffer sf = new StringBuffer();  
for (int i = 0; i < 100000; i++){  
    sf.append('a');  
}

// 可以拿这个玩一下10线程抢占
public static void StringBufferPool() throws InterruptedException{  
    String[] aToz = new String[]{  
            "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"  
    };  
  
    //10线程  
    Runnable task = ()->{  
        StringBuffer sb = new StringBuffer();  
  
        for(int i=0;i<10;i++){  
            sb.append(aToz[(int) (Math.random()*26)]);  
            System.out.println(Thread.currentThread().getName()+"当前字符:"+sb.toString());  
        }  
    };  
  
    ExecutorService es = Executors.newFixedThreadPool(10);  
    for (int k = 0; k< 10 ;k++){  
        es.execute(task);  
    }  
  
    es.shutdown();  
    es.awaitTermination(100000, TimeUnit.MILLISECONDS);  
}