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Tutorial Java Method Overloading


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So in the example below they want to give a example that multiple methods can have the same name with different parameters:

 

I have a few questions:

I thought variables had unique names, how does it knows we talk about the same x + y. I assume the variables are only defined within the method then, right? And not within the whole public class MyClass

 

Second: 

Why does the double return the value 10.5599999999999 instead of 10.56

If I edit 6.26 to 6.27 it will return 10.57

 

 

public class MyClass {
  static int plusMethodInt(int x, int y) {
    return x + y;
  }
  
  static double plusMethodDouble(double x, double y) {
    return x + y;
  }
  
  public static void main(String[] args) {
    int myNum1 = plusMethodInt(8, 5);
    double myNum2 = plusMethodDouble(4.3, 6.26);
    System.out.println("int: " + myNum1);
    System.out.println("double: " + myNum2);
  }
}
Result:
int: 13
double: 10.559999999999999
 
Third
Why call the method the same if your using different types of variables. Will  those variables called x be usable if you call on x and there is a value int 2 and float 4.21
Example in tutorial.
int myMethod(int x)
float myMethod(float x)
double myMethod(double x, double y)
Thank you
 
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This code below clarifies some part of my confusion in the first part of my question.

But the second and 3th question remains. 

public class MyClass {
  public static void main(String[] args) {

    // Code here CANNOT use x

    { // This is a block

      // Code here CANNOT use x

      int x = 100;

      // Code here CAN use x
      System.out.println(x);

   } // The block ends here

  // Code here CANNOT use x

  }
}
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To answer your float/double question, decimal numbers don't have infinite accuracy due to their representation in binary. As you can see you're 0.000000000001 out due to that. This is usually why choosing your data type and rounding appropriately are important. Different data types have different accuracies.

Your third question seems like there's something else underneath which you aren't asking. I'll answer it as generally as possible. Method Overloading like that is used for when you want to use one function for multiple different data types, or different amounts of them, and you require it to be handled differently per case.

Easiest way to see it in action is the '+' operator.

String x = "32" + "4";
System.out.println(x); // Outputs 324
int y = 2 + 4;
System.out.println(y); // Outputs 6

Two strings concatenate, two numbers add together. With an overload for every combination of data types that "+" can support.

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