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Java Forum / General / May 2007toString or typecast: which one is better
Object o = "Hello, World"; .... String x1 = o.toString(); // or String x2 = (String)o; ... which one will perform better? typecast or toString? > Object o = "Hello, World"; > .... [quoted text clipped - 4 lines] > > which one will perform better? typecast or toString? If it's just an object, then surely typecast will perform better. > Object o = "Hello, World"; > .... [quoted text clipped - 4 lines] > > which one will perform better? typecast or toString? Who cares? The chances of it making any difference to your overall algorithm are vanishingly small. Use the one that makes most sense in your code. Tom Hawtin Harish wrote On 05/07/07 14:16,: > Object o = "Hello, World"; > .... [quoted text clipped - 4 lines] > > which one will perform better? typecast or toString? String x3 = String.valueOf(o); ... gives you even more totally irrelevant and pointless performance questions to worry about. The thing you *ought* to care about is what effects the different approaches have. Try changing the first line to `Object o = null;' and observe that the three conversions to String yield three different results. Use the one whose results match what you want.  SignatureEric.Sosman@sun.com > Object o = "Hello, World"; > .... [quoted text clipped - 4 lines] > > which one will perform better? typecast or toString? I wouldn't be surprised if this wasn't optimized out by the compiler. Still, .toString() is probably safer because someone, at some point could change o to something other than a String. C> > Object o = "Hello, World"; > .... [quoted text clipped - 4 lines] > > which one will perform better? typecast or toString? There is a difference in the two, you can only cast if o really is a String object whereas you can call toString on any Object, not just a String. Will o always be a String? If so why not just use o rather than create x2? Can you change the design so that the compiler knows that o is a String? > Object o = "Hello, World"; > .... [quoted text clipped - 4 lines] > > which one will perform better? typecast or toString? talking about efficiency,no doubt typecast is better otherwise,the answer depends on what you gonna do with your code >> Object o = "Hello, World"; >> .... [quoted text clipped - 6 lines] > > talking about efficiency,no doubt typecast is better When it comes to questions of efficiency, *never* say "no doubt". Always measure. Typecasts are actually more complex than they might appear. In this case, because String is a final class, it's as simple as if (x2 == null) result is null else if (x2.getClass() == String.class) result is x2; else throw ClassCastException() but if String weren't final or were (God forbid) an interface, this logic would get more complicated. > Object o = "Hello, World"; > .... [quoted text clipped - 4 lines] > > which one will perform better? typecast or toString? If there's any chance of o being null, use the cast. Otherwise, you should thank God that everything else is working so well you can spend time on trivia like this. > Object o = "Hello, World"; > .... [quoted text clipped - 4 lines] > > which one will perform better? typecast or toString? String.valueOf(o) performs better than either of those, because it should never throw an exception! Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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