Double.valueOf(s) vs. Double.parseDouble [duplicate]

This question already has answers here: 开发者_JS百科 What is the difference between Double.parseDouble(String) and Double.valueOf(String)? (6 answers) Closed 9 years ago.

Casting an Object to a double and noticed both these methods. I see that parseDouble has been in since 1.2. Why add this method if it essentially does the same functionality as valueOf(s)?

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parseDouble() returns a primitive double value. valueOf() returns an instance of the wrapper class Double. Before Java 5 introduced autoboxing, that was a very significant difference (and many would argue it still is).

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Because it is not the same. valueOf() creates a Double object which is often not needed. parseDouble() does not. With autoboxing it's valueOf(String) which is no longer needed, but is therefore backward compatibility.

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If you just need the value (primitive) use parseDouble(String s) the cost is less. valueOf(String s) returns a Double class which wraps the primitive double value.