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POFastest way of converting integer to string in java
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  1. POFastest way of converting integer to string in java
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    copied!<p>Everytime I had to convert an <code>int</code>into a <code>String</code> I picked either <code>""+a</code>or <code>Integer.toString(a)</code>. Now I wondered which way is faster, so I wrote a simple benchmark that calls function_1, function_2 and function_3 10000000 times and prints how long it takes to process the functions. Here are the functions:</p> <pre><code>public static String i=""; public static String j=""; public static String k=""; public static void function_1() { i=Integer.toString(getOne()); } public static void function_2() { j=""+1; } public static void function_3() { j=""+getOne(); } public static int getOne() { return 1; } </code></pre> <p>the output is:</p> <pre><code>Benchmarking starting... Executing function_1 10000000 time(s)... Done executing function_1 in 476 ms. Executing function_2 10000000 time(s)... Done executing function_2 in 8 ms. Executing function_3 10000000 time(s)... Done executing function_3 in 634 ms. Benchmarking complete! </code></pre> <p>I think function_2 is so fast, because it is compiled as</p> <pre><code>public static void function_2() { j="1"; } </code></pre> <p>so to avoid that, I used the function <code>getOne()</code> instead. But here is the interesting part(for me): <code>function_3</code> must be compiled without using the original <code>toString</code> method of <code>Object</code>(in this case <code>Integer.toString(1)</code> because <code>int</code> is primitive). My question is: How does the compiler actually threat <code>""+1</code> so it is slower then calling <code>Integer.toString(1)</code>?</p>
 

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