Difference between valueOf and parseInt method in Java

Both valueOf and parseInt methods are used to convert String to Integer in Java, but there are subtle difference between them

If you look code of parseInt() and valueOf() method from java.lang.Integer class, you will find that actual job of converting String to integer is done by parseInt() method, valueOf() just provide caching of frequently used Integer objects, Here is code snippet from valueOf() method which makes things clear:

ublic static Integer valueOf(String s) throws NumberFormatException {
        return Integer.valueOf(parseInt(s, 10));
}

This method first calls parseInt() method, in order to convert String to primitive int, and then creates Integer object from that value. You can see it internally maintains an Integer cache. If primitive int is within range of cache, it returns Integer object from pool, otherwise it create a new object.

public static Integer valueOf(int i) {
        if(i >= -128 && i <= IntegerCache.high)
            return IntegerCache.cache[i + 128];
        else
            return new Integer(i);
}

There is always confusion, whether to use parseInt() or valueOf() for converting String to primitive int and java.lang.Integer, I would suggest use parseInt() if you need primitive int and use valueOf() if you need java.lang.Integer objects. Since immutable objects are safe to be pooled and reusing them only reduces load on garbage collector, it's better to use valueOf() if you need Integer object