String串拼接5种方式效率测试

在Java里String串的拼接方式有5种

join
concat
StringBuffer(线程安全)
StringBuilder

package com.main;
import java.util.ArrayList;
import java.util.List;
public class TestString {
     public void testPlus() {
         String s = "";
         long ts = System.currentTimeMillis();
         for (int i = 0; i < 50000; i++) {
             s = s + String.valueOf(i);
         }
         long te = System.currentTimeMillis();
         System.out.println("+ cost {"+ (te - ts)+"} ms");
     }
     public void testConcat() {
         String s = "";
         long ts = System.currentTimeMillis();
         for (int i = 0; i < 50000; i++) {
             s = s.concat(String.valueOf(i));
         }
         long te = System.currentTimeMillis();
         System.out.println("concat cost {"+ (te - ts)+"} ms");
     }
     public void testJoin() {
         List<String> list = new ArrayList<String>();
         long ts = System.currentTimeMillis();
         for (int i = 0; i < 50000; i++) {
             list.add(String.valueOf(i));
         }
         String.join("-", list);
         long te = System.currentTimeMillis();
         System.out.println("join cost {"+ (te - ts)+"} ms");
     }
     public void testStringBuffer() {
         StringBuffer sb = new StringBuffer();
         long ts = System.currentTimeMillis();
         for (int i = 0; i < 50000; i++) {
             sb.append(String.valueOf(i));
         }
         sb.toString();
         long te = System.currentTimeMillis();
         System.out.println("StringBuffer cost {"+ (te - ts)+"} ms");
     }
     public void testStringBuilder() {
         StringBuilder sb = new StringBuilder();
         long ts = System.currentTimeMillis();
         for (int i = 0; i < 50000; i++) {
             sb.append(String.valueOf(i));
         }
         sb.toString();
         long te = System.currentTimeMillis();
         System.out.println("StringBuilder cost {"+ (te - ts)+"} ms");
     }
     public void testStringBufferWith50000000() {
         StringBuffer sb = new StringBuffer();
         long ts = System.currentTimeMillis();
         for (int i = 0; i < 50000000; i++) {
             sb.append(String.valueOf(i));
         }
         sb.toString();
         long te = System.currentTimeMillis();
         System.out.println("StringBuffer50000000 cost {"+ (te - ts)+"} ms");
     }
     public void testStringBuilderWith50000000() {
         StringBuilder sb = new StringBuilder();
         long ts = System.currentTimeMillis();
         for (int i = 0; i < 50000000; i++) {
             sb.append(String.valueOf(i));
         }
         sb.toString();
         long te = System.currentTimeMillis();
         System.out.println("StringBuilder50000000 cost {"+ (te - ts)+"} ms");
     }
}

执行结果

+ cost {2789} ms
concat cost {1088} ms
join cost {8} ms
StringBuffer cost {4} ms
StringBuilder cost {3} ms
StringBuffer50000000 cost {3091} ms
StringBuilder50000000 cost {2726} ms