测试 StringBuffer

最新推荐文章于 2025-09-08 18:49:10 发布

mrAking

最新推荐文章于 2025-09-08 18:49:10 发布

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CC 4.0 BY-SA版权

文章标签：测试 string class

本文链接：https://blog.youkuaiyun.com/mrAking/article/details/6748390

本文详细介绍了Java中String Buffer和StringBuilder的使用方法、性能对比及应用场景，深入理解其内部实现原理。

public class TestStringBuffer {

   /**
   * @param args
   */
   public static void main(String[] args) {
       TestStringBuffer t = new TestStringBuffer();
       System.out.println();
       t.test0();
       // t.test1(); // 4203
       // t.test2(); // 0
       // t.test3(); // 4234
   }

   void test0() {
       String s1 = "xy123";
       s1 = "abcdef";
       s1 = new String("ABCDEFG");
       s1.replace('D', 'y');
       System.out.println(s1); // ABCDEFG 没变

       StringBuffer s2 = new StringBuffer("x");
       System.out.println(s2);
       s2.append(s1); // xabcdef
       s2.replace(2, 4, "_");
       System.out.println(s2);
       s2 = new StringBuffer(s1); // abcdef
       System.out.println(s2);

       String s3 = s1.substring(1, 3);// 截取index从第1个到第3个前面的 abcdef ==> bc
       System.out.println(s3); // bc

       StringBuilder s4 = new StringBuilder("ABCDEFGH-");
       s4.append(true);
       System.out.println(s4);       // ABCDEFGH-true
   }

   void test1() {
       String tempstr = "abcdefghijklmnopqrstuvwxyz";
       int times = 5000;
       long lstart1 = System.currentTimeMillis();
       String str = "";
       for (int i = 0; i < times; i++) {
           str += tempstr;
       }
       long lend1 = System.currentTimeMillis();
       long time = (lend1 - lstart1);
       System.out.println(time);

   }

   void test2() {
       String tempstr = "abcdefghijklmnopqrstuvwxyz";
       int times = 5000;
       long lstart2 = System.currentTimeMillis();
       StringBuffer sb = new StringBuffer();
       for (int i = 0; i < times; i++) {
           sb.append(tempstr);
       }
       long lend2 = System.currentTimeMillis();
       long time2 = (lend2 - lstart2);
       System.out.println(time2);

   }

   void test3() {
       String tempstr = "abcdefghijklmnopqrstuvwxyz";
       int times = 5000;
       long lstart2 = System.currentTimeMillis();
       String str = "";
       for (int i = 0; i < times; i++) {
           StringBuffer sb = new StringBuffer(str);
           sb.append(tempstr);
           str = sb.toString();
       }
       long lend2 = System.currentTimeMillis();
       long time2 = (lend2 - lstart2);
       System.out.println(time2);

   }
}