string stringbuffer stringbuilder区别

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 {
@Test
public 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. ");
}

@Test
public 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. ");
}

@Test
public 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. ");
}
}