055.154-Which statement is true?

[theoffspring]

Given this method in a class:

21. public String toString() {
22. StringBuffer buffer = new StringBuffer();
23. buffer.append('<');
24. buffer.append(this.name);
25. buffer.append('>');
26. return buffer.toString();
27. }

Which statement is true?

A. This code is NOT thread-safe.
B. The programmer can replace StringBuffer with StringBuilder with no other changes.
C. This code will perform poorly. For better performance, the code should be rewritten:
return "<" + this.name + ">";
D. This code will perform well and converting the code to use StringBuilder will not enhance the
performance.

Answer: B


我认为A是对的，StringBuffer虽是线程安全的，但这段代码却不是线程安全的，如果是在单线程中使用，选B当然是可以的

[swandragon]

buffer是局部变量，每次调用方法都生成新的对象
所以A不对

[lxxzhy]

A是不对的.

StringBuffer buffer = new StringBuffer();
是在toString方法里面定义的本地变量,是线程安全的.