Java 字符串拼接方式

import java.util.ArrayList; 
import java.util.List; 

import org.apache.commons.lang.StringUtils; 
import org.junit.Test; 
import org.slf4j.Logger; 
import org.slf4j.LoggerFactory; 

public class TestString { 

    private final Logger logger = LoggerFactory.getLogger(this.getClass()); 

    @Test 
    public void testPlus() { 
        String s = ""; 
        long ts = System.currentTimeMillis(); 
        for (int i = 0; i < 10000; i++) { 
            s = s + String.valueOf(i); 
        } 
        long te = System.currentTimeMillis(); 
        logger.info("+ cost {} ms", te - ts); 
    } 

    @Test 
    public void testConcat() { 
        String s = ""; 
        long ts = System.currentTimeMillis(); 
        for (int i = 0; i < 10000; i++) { 
            s = s.concat(String.valueOf(i)); 
        } 
        long te = System.currentTimeMillis(); 
        logger.info("concat cost {} ms", te - ts); 
    } 

    @Test 
    public void testJoin() { 
        List<String> list = new ArrayList<String>(); 
        long ts = System.currentTimeMillis(); 
        for (int i = 0; i < 10000; i++) { 
            list.add(String.valueOf(i)); 
        } 
        StringUtils.join(list, ""); 
        long te = System.currentTimeMillis(); 
        logger.info("StringUtils.join cost {} ms", te - ts); 
    } 

    @Test 
    public void testStringBuffer() { 
        StringBuffer sb = new StringBuffer(); 
        long ts = System.currentTimeMillis(); 
        for (int i = 0; i < 10000; i++) { 
            sb.append(String.valueOf(i)); 
        } 
        sb.toString(); 
        long te = System.currentTimeMillis(); 
        logger.info("StringBuffer cost {} ms", te - ts); 
    } 

    @Test 
    public void testStringBuilder() { 
        StringBuilder sb = new StringBuilder(); 
        long ts = System.currentTimeMillis(); 
        for (int i = 0; i < 100000; i++) { 
            sb.append(String.valueOf(i)); 
        } 
        sb.toString(); 
        long te = System.currentTimeMillis(); 
        logger.info("StringBuilder cost {} ms", te - ts); 
    } 
}

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