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Thread: Multiple Class Calculator

  1. #1
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    Default Multiple Class Calculator

    I am trying to write a Calculator. I must write the operations in one Class and the result in another. So this is what i did...

    public class Calc {
     
    	calc_main c=new calc_main();
    	private int add;
    	private int sub;
    	private int mul;
    	private int div;
     
    	public Calc(){
    		add=0;
    		sub=0;
    		mul=0;
    		div=0;
    	}
    	public void adder(int adds){
    	adds=c.number1+c.number2;
    	add=adds;
    	}
    	public int added(){
    		return add;
    		}
     
    	public void suber(int subs){
    	subs=c.number1-c.number2;
    	sub=subs;
    	}
    	public int subed(){
    		return sub;
    		}
     
    	public void muler(int muls){
    	muls=c.number1*c.number2;
    	mul=muls;
    	}
    	public int muled(){
    		return mul;
    		}
     
    	public void diver(int divs){
    	divs=c.number1/c.number2;
    	div=divs;
    	}
    	public int dived(){
    		return div;
    		}
    }

    public class calc_main {
     
    	public int number1;
    	public int number2;
    	public String oper;
     
    	public calc_main(){
    	Scanner num=new Scanner(System.in);
     
    	System.out.println("Enter first number:");
    		number1=num.nextInt();
    	System.out.println("Enter operation:");
    		oper=num.next();
    	System.out.println("Enter second number:");
    		number2=num.nextInt();
    	}
    }
     
    	public static void main(String[] args) {
    		calc_main c=new calc_main();
    		Calc r=new Calc();
    		if(c.oper=="+")
    			System.out.println(c.number1+"+"+c.number2+"="+r.added());
    		else if(c.oper=="-")
    			System.out.println(c.number1+"-"+c.number2+"="+r.subed());
    		else if(c.oper=="*")
    			System.out.println(c.number1+"*"+c.number2+"="+r.muled());
    		else if(c.oper=="/")
    			System.out.println(c.number1+"/"+c.number2+"="+r.dived());
     
    	}
    There are no errors in any lines. But when i run it, it asks me to enter the numbers and operator twice and just stop.


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Multiple Class Calculator

    and just stop.
    Does that mean the program exits?
    Try debugging the code by adding some println statements in the methods that are called so you can see where the execution flow is going. Print out a message when each method is entered and when it exits. That will show you what methods are being executed and in what order. If a message isn't printed, then you know that the method was not called.


    Also add an else statement at the end of the if/else if chain to print a message saying none of the if above statements were true.

    One problem I see is the use of == to compare Strings. The code needs to use the equals() method.
    If you don't understand my answer, don't ignore it, ask a question.

  3. #3
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    Default Re: Multiple Class Calculator

    The two inputs results from the two constructor calls(you make the input operation in the constructor):
    First:
    public static void main(String[] args) {
    		calc_main c=new calc_main();

    and second:

    public class Calc {
     
    	calc_main c=new calc_main();

    Be careful, you now use two calc_main objects. With the first - in the main method - you check the calculation option with the second one - class var in Calc - you do some way of calculation, I think.

    BTW Thanks for the thread. I someway thought that due to the switch-string feature in java 1.7 the string comparisons now work in the == way. Dont know why.
    I use java 1.6 at the moment but this thread prevents me making bad mistakes in future

  4. #4
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    Default Re: Multiple Class Calculator

    Thanks guys. thanks to your advice i fixed my problems.
    with println debug i realized that operation performing objects were not called. so i fixed that.
    and asking to enter numbers twice was because i called the calc_main object twice.

    also glad to be help, even thou i had no idea about it

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