java中拼接字符串的5种方法效率对比

前言

最近写一个小编,可能会考虑到字符串拼接,想了几种方法,但对性能未知，所以下面就来测试下面，话不多说了，来一起看看详细的介绍吧。

示例代码

public class Test {
  List<String> list = new ArrayList<>();
  @Before
  public void init(){
    IntStream.range(0,100000).forEach((index) -> {
      list.add("str" + index);
    });
  }
  @org.junit.Test
  public void test1() {
    String ss = "";
    long startTime = System.currentTimeMillis();
    for (String s : list) {
      ss += s;
    }
    System.out.println(System.currentTimeMillis() - startTime);
  }
  @org.junit.Test
  public void test2() {
    String ss = "";
    long startTime = System.currentTimeMillis();
    for (String s : list) {
      ss=ss.concat(s);
    }
    System.out.println(System.currentTimeMillis() - startTime);
  }
  @org.junit.Test
  public void test3() {
    StringBuilder ss = new StringBuilder();
    long startTime = System.currentTimeMillis();
    for (String s : list) {
      ss.append(s);
    }
    System.out.println(System.currentTimeMillis() - startTime);
  }
  @org.junit.Test
  public void test4() {
    long startTime = System.currentTimeMillis();
    StringUtils.join(list);
    System.out.println(System.currentTimeMillis() - startTime);
  }
  @org.junit.Test
  public void test5() {
    StringBuffer ss = new StringBuffer();
    long startTime = System.currentTimeMillis();
    for (String s : list) {
      ss.append(s);
    }
    System.out.println(System.currentTimeMillis() - startTime);
  }
}