String,StringBuffer与StringBuilder对比

1.拼接字符串性能对比

StringBuilder > StringBuffer > String

public class stringTest {public static void main(String[] args) {StringBuffer sb = new StringBuffer();StringBuilder sd = new StringBuilder();String s = "123";Long ap = System.currentTimeMillis();for(int i = 0 ; i < 100000;i++){sb.append(s);}System.out.println("StringBuffer:"+(System.currentTimeMillis()-ap)+"ms");Long sdd = System.currentTimeMillis();for(int i = 0 ; i < 100000;i++){sd.append(s);}System.out.println("StringBuilder:"+(System.currentTimeMillis()-sdd)+"ms");Long st = System.currentTimeMillis();for(int i = 0 ; i < 100000;i++){s = s+"123";}System.out.println("String:"+(System.currentTimeMillis()-st)+"ms");}}

2. StringBuilder不保证线程安全，StringBuffer线程安全