从源码看StringBuilder和StringBuffer

StringBuilder和StringBuffer

结论：StringBuilder是线程不安全的、StringBuffer是线程安全的

StringBuilder和StringBuffer是比String高效的应为他是在原来的字符上进行增加的

public class StringBufferAndBuilder {
    static StringBuffer stringBuffer = new StringBuffer();
    static StringBuilder stringBuilder = new StringBuilder();
    public static void main(String[] args) {
        StringBufferAndBuilder main = new StringBufferAndBuilder();
        ThreadStringTest threadStringTest =  main.new ThreadStringTest();
        //创建3个线程加数据
        new Thread(threadStringTest).start();
        new Thread(threadStringTest).start();
        new Thread(threadStringTest).start();
        try {
            //等待4秒三个线程全部运行完
            Thread.sleep(4);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println("stringBuffer的长度"+stringBuffer.length());
        System.out.println("============");
        System.out.println("stringBuffer的长度"+stringBuilder.length());
    }
    class ThreadStringTest implements Runnable{
        @Override
        public void run() {
            for (int i = 0; i  
查看源代码
 
StringBuffer的append方法是使用了synchronized修饰
 
    @Override
    public synchronized StringBuffer append(int i) {
        toStringCache = null;
        super.append(i);
        return this;
    }
 
StringBuilder的append方法没有同步代码块所以线程不安全
 
    @Override
    public StringBuilder append(int i) {
        super.append(i);
        return this;
    }