StringBuilder和Stringbuffer

StringBuilder的append方法

    @Override    public StringBuilder append(Object obj) {        return append(String.valueOf(obj));    }    @Override    public StringBuilder append(String str) {        super.append(str);        return this;    }

StringBuffer的append方法

    @Override    public synchronized StringBuffer append(Object obj) {        toStringCache = null;        super.append(String.valueOf(obj));        return this;    }    @Override    public synchronized StringBuffer append(String str) {        toStringCache = null;        super.append(str);        return this;    }