string stringbuffer stringbuilder区别

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stringbuffer ：A thread-safe, mutable sequence of characters。

stringbuilder：Instances of StringBuilder are not safe for use by multiple threads。这个就是stringbuffer和stringbuilder的主要区别，其他基本的操作是相同的。

stringbuilder 现在多用在Hibernate 条件拼装(因为Hibernate的session是单例的)。

string 多用于字段属性，还有字符串处理

stringbuffer,stringbuilder,string 性能测试

import org.junit.Test;public class TestString {@Testpublic void testString(){String base = " base string. ";int count = 2000000;long begin, end;begin = System.currentTimeMillis();String test = new String(base);for (int i = 0; i < count/100; i++) {test = test + " add ";}end = System.currentTimeMillis();System.out.println((end - begin) +" millis has elapsed when used String. ");}@Testpublic void testStringBuffer(){String base = " base string. ";int count = 2000000;long begin, end;begin = System.currentTimeMillis();StringBuffer test = new StringBuffer(base);for (int i = 0; i < count/100; i++) {test.append(" add ");}end = System.currentTimeMillis();System.out.println((end - begin) +" millis has elapsed when used String. ");}@Testpublic void testStringBuilder(){String base = " base string. ";int count = 2000000;long begin, end;begin = System.currentTimeMillis();StringBuilder test = new StringBuilder(base);for (int i = 0; i < count/100; i++) {test.append(" add ");}end = System.currentTimeMillis();System.out.println((end - begin) +" millis has elapsed when used String. ");}}

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