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up vote 7 down vote favorite
1

Sometimes there is need to change an integer to text. I often use the following way:

"" + myNumber

But there is alternative way:

Integer.toString(myNumber)

Which one is better (performance, readability, safety)? Or are those equal?

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3  
A very detailed answer to a very similar question on SO: stackoverflow.com/a/4105406/843804 –  palacsint Jul 18 '12 at 17:11

3 Answers 3

up vote 15 down vote accepted

I would recommend

String.valueOf(myNumber)

This allows you to to change myNumber to another primitive type - or a Number - later.

"" + myNumber

should be avoided since :

  • it produces clutter bytecode (instanciating a new StringBuffer)
  • it does not convey what you wanted to do with myNumber
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up vote 11 down vote

Integer.toString(myNumber) is the safer way because it throws a malformed exception.

Do not worry about performance at this level. There is an expression: Premature Optimization.

EDIT after comment

"3000000000" > Integer.MAX_VALUE throw an Exception
"-2900000000" < Integer.MIN_VALUE throw an Exception
"OO12345" throw an exception, because it begins with two O letters, not zero.

You can also manage radix :

String intS = "010101";
System.out.format("Parsing %s gives %d, fail with \"010102\"%n",
    intS,(Integer.parseInt(intS, 2)));
intS = "10CAFE8";
System.out.format("Parsing %s gives %d, fail with \"10CAGE8\"%n",
    intS,(Integer.parseInt(intS, 16)));

Output :

Parsing 010101 gives 21, fail with "010102"
Parsing 10CAFE8 gives 17608680, fail with "10CAGE8"

EDIT after comment 2

Look in Effective Java and search for StringBuilder() to understant how to replace '+' usage.

At execution time, a '+' create something like this code :

StringBuilder sb = new StringBuilder();
sb.append(123);
sb.toString();

This code is better :

final int a = 123;
Integer.toString(a);

Look at Java code of Integer.toString(a);
In Eclipse : CTRL+rightClick on toString() print the Java code . Give the src.zip path in SDK directory if it not already done.
And compare with StringBuilder.append(int);

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4  
How can an integer be malformed? –  Felix Dombek Jul 18 '12 at 16:35
    
@FelixDombek I've edited my post to give samples. –  cl-r Jul 19 '12 at 9:57
3  
Your examples are about String to Int, but the question is about Int to String. –  Felix Dombek Jul 19 '12 at 13:05
    
@FelixDombek Exact, I compelte my post. Sorry not to be a good english reader. –  cl-r Jul 20 '12 at 6:07
    
@FelixDombek Effective Java is a reference to write good code, Is the response you needed? Many other things to know are also inside this book. –  cl-r Jul 21 '12 at 15:50
up vote 1 down vote

I would say they were equally as good. I prefer to use

Integer.toString(myNumber)

as I find it explains the transition better

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haha my mistake @palacsint –  IronSpoon Jul 20 '12 at 8:54

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