最近看到一篇介紹字符串拼接的介紹,感覺不錯,轉載一下:
代碼如下:
- 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);
- }
- }
運行結果如下:
11:00:22,359 INFO TestString:23 - + cost 1828 ms
11:00:22,921 INFO TestString:34 - concat cost 562 ms
11:00:22,937 INFO TestString:46 - StringUtils.join cost 16 ms
11:00:22,968 INFO TestString:58 - StringBuffer cost 31 ms
11:00:23,031 INFO TestString:70 - StringBuilder cost 63 ms
要特別注意的是:
StringBuilder 循環的次數是其它的10倍,如果是一樣,那麼返回 0,可見StringBuilder 的速度之快。
總結:
用+的方式效率最差,concat由於是內部機制實現,比+的方式好了不少。
Join 和 StringBuffer,相差不大,Join方式要快些,可見這種JavaScript中快速拼接字符串的方式在Java中也非常適用。
StringBuilder 的速度最快,但其有線程安全的問題