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I am using the following approach to convert any primitive data type to string

Example

int i = 5;//
String convertToString = ""+i;// convert any primitive data type to string

To convert int data type to string i can use Integer.toString() but what is the better way to convert any type of primitive data (not only int) types to string

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4
  • 1
    Doesn't everything in Java have .toString() method? Commented Dec 26, 2011 at 11:48
  • 1
    @SergeiTulentsev primitives don't Commented Dec 26, 2011 at 11:51
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    primitive types are not objects so they don't have toString() Commented Dec 26, 2011 at 11:51
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    jeezz.. primitives surely don't have any methods, I was just answering @SergeiTulentsev question, because in the above example toString() can't be applied to primitive type int Commented Dec 26, 2011 at 11:54

4 Answers 4

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43

Use String.valueOf() method.

int no = 2;

String strValue = String.valueOf( no );
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11 Comments

@HarryJoy Which one? Do you mean string concatenation or toString()
The main adavantage is that there is a String.valueOf method for boolean, char, int, long, float, double and Object, so the same method name can be used to convert anything to a String.
@JBNizet : I'm not against valueOf() method. Actually I'm curious about why this is the best/better to use among all conversion methods?
It's better, because it creates one new String instance instead three. ""+i is probably translated into "".concat(String.valueOf(1));
Advantage is: it creates string in the reusable string literal pool.
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5

I recently ran some benchmarks to compare ""+myInt vs Integer.toString(myInt).

And the winner is... Integer.toString() !

Because it does not create temporary strings, uses only a adequately-sized char buffer, and some funky algorithms to convert from a digit to its char counterpart.

Here is my blog entry if you read french (or use the sidebar translation widget if you don't)

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Comments

3

Consider this example :

int i = 42; 
\\ String 
str = Integer.toString(i);

In this case you could also do :

String str = "" + i;

Similarly, one of the easiest way to convert primitive datatypes to String is to use the toString() method with the datatype object of the element to be converted.

 String str = Double.toString(d); // Convert double to String
 String str = Long.toString(l);  //Convert long to String
 String str = Float.toString(f); //Convert float to String
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1

You need to define "better". The most efficient way for the machine is to use

String.valueOf(no);

or

Integer.toString(no);

however the most efficient use of your time is to make the code as simple as possible.

"" + no;

This is fairly hot contested decision which reminds me of this quote

DEVENTER (n) A decision that's very hard to make because so little depends on it, such as which way to walk around a park

-- The Deeper Meaning of Liff by Douglas Adams and John Lloyd.

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11 Comments

Will you please care to explain "Why String.valueOf(no); is the most efficient way for the machine?"
+1 Even though it's "hackalicious", I favour no + "" for its brevity and clarity
I don't find it clear. String.valueOf() and Integer.toString() express the intention clearly. no + "" doesn't, IMHO.
"a" + no. But in this case, the intent is to concatenate. Not to convert.
With PMD becoming a standard tool in Java development, this idiom is less and less frequent, because PMD has a rule to avoid it: pmd.sourceforge.net/rules/optimizations.html#AddEmptyString
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