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; publicclassTestString{ privatefinal Logger logger = LoggerFactory.getLogger(this.getClass()); @Test publicvoidtestPlus(){ 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 publicvoidtestConcat(){ 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 publicvoidtestJoin(){ 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 publicvoidtestStringBuffer(){ 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 publicvoidtestStringBuilder(){ 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); } }
结果:
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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