Hey guys, I got such great help last time I decided to come back for more :). Hope I'm not bothering with these questions, my teacher isn't much for being nice or explaining..

Right now we are getting into methods, I know that they aren't that difficult but I for the life of me can't seem to wrap my head around them.

I know that we have the main method, and then methods after that are user created. What I don't understand is how I send variables to the user created methods, and when to initialize or if I need to multiple times since the methods are separate. I know how to return the variables, that's easy enough.

Thanks.

Simple examples

public class SimpleMethods{
	
	public int additionMethod(int x, int y){
		int c = x + y;
		return c;
	}
	
	public int subtractionMethod(int a, int b){
		return a - b;
	}
	
	public int multiplicationMethod(int a, int b){
		return a * b;
	}
	
	public int divisionMethod(int a, int b){
		return a / b;
	}
	
	public int modulusMethod(int a, int b){
		return a % b;
	}
}
public class MethodsExample{
	private static SimpleMethods simpleMethods = new SimpleMethods();
	
	public static void main(String[] args){
		int a = 8;
		int b = 4;
		
		System.out.println("multiplication of a by number 10 is " + multiplicationByTen(a));
		
		int c = simpleMethods.additionMethod(a, b);
		System.out.println("c = "+c);
		
		System.out.println("subtraction of a and b is "+ simpleMethods.subtractionMethod(a, b));
		System.out.println("multiplication of a and b is "+ simpleMethods.multiplicationMethod(a, b));
		System.out.println("division of a and b is "+ simpleMethods.divisionMethod(a, b));
		System.out.println("modulus of a and b is "+ simpleMethods.modulusMethod(a, b));
		
		callAllMethods(a, b);
	}
	
	public static int multiplicationByTen(int a){
		return a * 10;
	}
	
	public static void callAllMethods(int a, int b){
		System.out.println("call from callAllMethods - addition of a and b is "+ simpleMethods.additionMethod(a, b));
		System.out.println("call from callAllMethods - subtraction of a and b is "+ simpleMethods.subtractionMethod(a, b));
		System.out.println("call from callAllMethods - multiplication of a and b is "+ simpleMethods.multiplicationMethod(a, b));
		System.out.println("call from callAllMethods - division of a and b is "+ simpleMethods.divisionMethod(a, b));
		System.out.println("call from callAllMethods - modulus of a and b is "+ simpleMethods.modulusMethod(a, b));
	}
}
  • First method call ( multiplicationByTen(a) )is on a method that is accessible inside MethodsExample class.
  • Second method call ( simpleMethods.additionMethod(a, b) ) is on a method that is available through simpleMethods instance of class SimpleMethods. Here you can see that result of the method can be assigned to a variable and can be used later on by caller method or class depending on variable declaration (local/global)
  • At the end you will find method call ( callAllMethods(a, b) ) that will call method callAllMethods that inside it body will call methods of simpleMethods instance to demonstrate that you can call methods from a methods and you can call it as many times you need it

Hope this helps

Ok I think I understand. I tried to use a method to find out if a number is prime or not, but I don't think I did it correctly. The program just keeps running if the number is not prime.

import java.util.Scanner;
public class prime   
{
public static void main (String[] args)
{
    Scanner keyboard = new Scanner(System.in);
    System.out.println("please enter a num");
    int num= keyboard.nextInt();       

    boolean flag= isPrime(num);
    System.out.println(flag);
}

public static boolean isPrime (int num)
{
    int i=2;
    boolean flag=true;
    
    while ((i<num/2)&&(flag=true))
        {
            if (num%i==0)
                flag=false;
             
            else i++;
            }
            
            return flag;
}
}

Ah I see. Stupid little mistakes.

I think overall I understand methods, but I was confused today when my professor told us that it doesn't matter what parameters you give a method when calling it, how does that work?

I think that is probably only a part of his statement, because without any context of the discussion that doesn't make any sense.

If you mean method overloading than it is this

public void addNumbers(double a, double b){
//code here
}

public void addNumbers(int a, int b){
//code here

/**
* Somewhere in the class
*/
double x = 2.1;
double y = 2.3;
double z = addNumbers(x,y);

int k = addNumbers(5, 7);
}
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