StringBuffer、StringBuilder区分
StringBuffer与 StringBuilder中的要领和功用完全是等价的,只是StringBuffer中的要领多数采纳了synchronized关键字举行润饰,因此是线程平安的,支撑并发操纵,合适多线程中运用。StringBuilder不支撑并发操纵,线性不平安的,不合适多线程中运用。新引入的StringBuilder类不是线程平安的,但其在单线程中的性能比StringBuffer高。(引荐进修:JAVA视频教程)
接下来,我直接贴上测试历程和效果的代码,一览无余:
public class StringTest { public static String BASEINFO = "Mr.Y"; public static final int COUNT = 2000000; /** * 实行一项String赋值测试 */ public static void doStringTest() { String str = new String(BASEINFO); long starttime = System.currentTimeMillis(); for (int i = 0; i < COUNT / 100; i++) { str = str + "miss"; } long endtime = System.currentTimeMillis(); System.out.println((endtime - starttime) + " millis has costed when used String."); } /** * 实行一项StringBuffer赋值测试 */ public static void doStringBufferTest() { StringBuffer sb = new StringBuffer(BASEINFO); long starttime = System.currentTimeMillis(); for (int i = 0; i < COUNT; i++) { sb = sb.append("miss"); } long endtime = System.currentTimeMillis(); System.out.println((endtime - starttime) + " millis has costed when used StringBuffer."); } /** * 实行一项StringBuilder赋值测试 */ public static void doStringBuilderTest() { StringBuilder sb = new StringBuilder(BASEINFO); long starttime = System.currentTimeMillis(); for (int i = 0; i < COUNT; i++) { sb = sb.append("miss"); } long endtime = System.currentTimeMillis(); System.out.println((endtime - starttime) + " millis has costed when used StringBuilder."); } /** * 测试StringBuffer遍历赋值效果 * * @param mlist */ public static void doStringBufferListTest(List<String> mlist) { StringBuffer sb = new StringBuffer(); long starttime = System.currentTimeMillis(); for (String string : mlist) { sb.append(string); } long endtime = System.currentTimeMillis(); System.out.println(sb.toString() + "buffer cost:" + (endtime - starttime) + " millis"); } /** * 测试StringBuilder迭代赋值效果 * * @param mlist */ public static void doStringBuilderListTest(List<String> mlist) { StringBuilder sb = new StringBuilder(); long starttime = System.currentTimeMillis(); for (Iterator<String> iterator = mlist.iterator(); iterator.hasNext();) { sb.append(iterator.next()); } long endtime = System.currentTimeMillis(); System.out.println(sb.toString() + "builder cost:" + (endtime - starttime) + " millis"); } public static void main(String[] args) { doStringTest(); doStringBufferTest(); doStringBuilderTest(); List<String> list = new ArrayList<String>(); list.add(" I "); list.add(" like "); list.add(" BeiJing "); list.add(" tian "); list.add(" an "); list.add(" men "); list.add(" . "); doStringBufferListTest(list); doStringBuilderListTest(list); } }
看一下实行效果:
2711 millis has costed when used String. 211 millis has costed when used StringBuffer. 141 millis has costed when used StringBuilder. I like BeiJing tian an men . buffer cost:1 millis I like BeiJing tian an men . builder cost:0 millis
从上面的效果能够看出,不斟酌多线程,采纳String对象时(我把Count/100),实行时间比其他两个都要高,而采纳StringBuffer对象和采纳StringBuilder对象的差异也比较显著。因而可知,假如我们的顺序是在单线程下运转,或者是没必要斟酌到线程同步题目,我们应当优先运用StringBuilder类;假如要保证线程平安,自然是StringBuffer。
从背面List的测试效果能够看出,除了对多线程的支撑不一样外,这两个类的运用体式格局和效果几乎没有任何差异。
更多JAVA相干技术文章,请接见JAVA开辟教程栏目举行进修!
以上就是stringbuffer和stringbuilder的区分的细致内容,更多请关注ki4网别的相干文章!