Is this the correct way to convert a char to a String in Java? [duplicate]

Question

While writing unit tests for a function returning boolean that takes two Strings, and I needed to test every character of the alphabet ('a'-'z') in sequence as one of the parameters, one-by-one, so I wrote this to do that:

for(char c = 'a'; c <= 'z'; c++) {     assertTrue(MyClass.MyFunction(testSubject, new String(c)); }  

I would have thought this was permissible, but it wasn't, so I just did it like this instead:

for(char c = 'a'; c <= 'z'; c++) {     assertTrue(MyClass.MyFunction(testSubject, ((Character) c).toString()); }  

Is this a reliable method to convert a char to a String in Java? Is it the preferred way? I don't know a whole lot about Java so would like some clarification on this.

Answer 1

The shortest solution:

char c = 'a'; String s = "" + c; 

The cleanest (and probably most efficient¹) solutions:

char c = 'a';  String s1 = String.valueOf(c); // or String s2 = Character.toString(c); 

Compared to your approach, the above prevents the overhead of having to box the primitive into a Character object.

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^{1 The slight inefficiency of the string concatenation in the first approach might be optimized away by the compiler or runtime, so one (if one were so inclined) would really have to run a micro-benchmark to determine actual performance. Micro-optimizations like this are rarely worth the effort, and relying on concatenation to force string conversion just doesn't look very nice.}