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    <p>The <code>+=</code> operator of String in fact create a new instance of a String instead of modifying your original string object. In other words, the following two lines of code are equivalent:</p> <pre><code>s += "Gotcha" s = new String(s + "Gotcha"); </code></pre> <hr> <p><em><strong>Example</em></strong></p> <p>Below is an example doing something similar to your <code>doSomeThing</code></p> <pre><code>public class st { public static void main(String[] args) { String hello = "hello"; String helloReference = hello; // making helloReference and hello refer to same object. helloReference += " world"; // perform += System.out.format("`hello` = %s, `helloReference` = %s\n", hello, helloReference); } } </code></pre> <p>and its output is the following, which shows that the object referred by <code>hello</code> is not affected by the <code>+=</code> operator performed by <code>helloReference</code>:</p> <pre><code>hello = `hello`, helloReference = `hello world` </code></pre> <p>In other world, before the += operator:</p> <pre><code> hello helloReference | | ------------------------------- | "hello" | ------------------------------- </code></pre> <p>after the += operator, it will create an new instance and modify the object which <code>helloReference</code> referenced to:</p> <pre><code> hello helloReference | | -------------------- | --------------| "hello world" | ------------------------------- -------------------- | "hello" | ------------------------------- </code></pre> <hr> <p>So your code is safe to go, the action performed in you doSomeThing will affect the objects referred by your SomeClass:</p> <pre><code>public class DoSomething { for (String s : SomeClass.getSomeList()){ // this create an new string instance to s s+="Gotcha"; } } </code></pre>
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    1. COwhat your saying is that java passes references not pointers. Is there a way to pass a pointer in Java (That's the C programmer in me talking...). And +1 for the text graphics.
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    2. COjust the `=` can pass the reference in Java, the difference is the immutability of `String`, which will create a new instance when necessary.
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    3. COFor those classes which are designed immutable, you have no way to change it after its creation.
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