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    <p>Java's parameter passing is quite tricky - When an object is passed to a function, you can manipulate the object's fields but you cannot manipulate object itself. The object reference is passed by value. So, you can say:</p> <pre><code>class someClass{ int i = 5; } class Foo { static void func(someClass c) { c.i = 3; } } class MainClass{ public static void main(){ someClass c = new someClass(); System.out.println(c.i); Foo.func(c); System.out.println(c.i); } } </code></pre> <p>Expect your output to be:</p> <pre><code>5 3 </code></pre> <p>Changes to the fields of c persist.</p> <p>but if manipulate the object itself, this manipulation will only persist in <code>Foo.func()</code> and not outside that function:</p> <pre><code>class someClass{ int i = 5; } class Foo { static void func(someClass c) { c.i = new someClass(); c.i = 3; System.out.println(c.i); } } class MainClass{ public static void main(){ someClass c = new someClass(); System.out.println(c.i); Foo.func(c); System.out.println(c.i); } } </code></pre> <p>Expect your output to be:</p> <pre><code>5 3 5 </code></pre> <p>What has happened? c.i has the value 5 in <code>MainClass.main()</code> in <code>Foo.func()</code>, c itself is modified to point to another instance of <code>someClass</code>, containing the value 3. However, this change is not reflected to the actual object that has been passed. The <code>c</code> in <code>Foo.func()</code> and <code>MainClass.main()</code> are different objects now. That's why changes to the <code>c</code> of <code>Foo.func()</code> do not affect the <code>c</code> in <code>MainClass.main()</code>.</p>
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    1. POJava supports pass-by-value. But can't make out the reason of the below code
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    1. USMax Beikirch
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    1. COWhy complicate things? There is nothing tricky here. Just simple definitions.
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    2. CO@Vitaly: I find it rather confusing that one can change the properties of an object in a function but not the object itself. I don't understand why `p.i = 3` and `p = new object()` should have different effects - although I understand why they do technically. Java is annoying :D
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    3. COThis adds simplicity actually, a caller always sure that callee will not change the object reference. Things are much more complicated in C++ where there are a lot of things around parameters.
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