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javastringstringbuilderstringbuffer

Why does java have StringBuilder or StringBuffer?

There are many differences between String and (StringBuilder or StringBuffer) like mutability and many string operations

May be this question seems a bit silly, but I want to know for the sake of programming paradigm.

I want to ask, why has Java implemented another class, StringBuilder or StringBuffer for a data structure like String. Why have they not given those features in String itself.

Why not make String itself thread-safe or provide some extra features that StringBuilder or StringBuffer has?

Solution

    1. String is immutable and there are many reason and also benefit to it. Why? and what the necessity of it? (very popular topic ) search or read those why-is-string-immutable-in-java or why-string-is-immutable-in-java

    2. Now Some one need to do frequent String operation here comes StringBuffer which is thread safe (synchronized).

    3. Some one don't need thread safety here comes StringBuilder.

    Now some one can still use StringBuffer when thread safety is not necessary, but that would be slow. That's why both of them is important.

    String's are differently handled by jvm If those features of StringBuffer was added it will not be immutable any more.

    Update : point 2 and 3 are altered from the comment of @Jon Skeet.