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Java Help

Mimikyu

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Donald-Duck

I think you ended your main bracket too late, you meant to end it after your if/else I assume? But its actually ended after the first function.

= is for setting variables, while == is the comparison operator. To compare characters you have to do for example
if(variable == 'A') for the letter A

there is no else(condition) theres only
else {
}
and
if else () {
}

Format your closing brackets better - it'll save you a lot of time if you line them up correctly

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

char option;
System.out.print("Please choose one of the following:");
System.out.print("(A)	Add");
System.out.print("(B)	Subtract");
option=keyboard.readChar ();

	if (option=A){	
		add();
	}

	else (option=B) { 	
		subtract();
	}




static void add(){
	int number1, number2;

	System.out.println("Please enter two numbers to add:   ");
	number1 = Keyboard.readInt();
	number2 = Keyboard.readInt();
	System.out.println("Your answer is:");
	System.out.println(number1 + number2);
}


} 

static void subtract(){
	int number3, number4,

	System.out.println("Please enter two numbers to subtract:   ");
	number3 = Keyboard.readInt();
	number4 = Keyboard.readInt();
	System.out.println("Your answer is:");
	System.out.println(number3 - number4);

}

}

Theres the brackets realigned in a clearer way - it should help show you were you have too many

omb0wyn5ehpij9

Are you in IT Tallaght by any chance?! I had that exact assignment in 1st year

dlofnep

You forgot to close off your variables.

int number3, number4,

That should be a semi-colon instead of a comma.

Also, use switch cases for menus, not if statements.

Mimikyu

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Donald-Duck

For comparing chars you use the apostraphe key instead of quotes and your main still ends in the wrong place, its ending after your add function instead of before

Mimikyu

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Donald-Duck

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

char option;
System.out.print("Please choose one of the following:");
System.out.print("(A)	Add");
System.out.print("(B)	Subtract");
option=keyboard.readChar ();

switch (option) {
	case "A": add();
	case "B" subtract();
}


[b] but I'm pretty sure you want it to end here[/b]

	static void add(){
		int number1, number2;

		System.out.println("Please enter two numbers to add:   ");
		number1 = Keyboard.readInt();
		number2 = Keyboard.readInt();
		System.out.println("Your answer is:");
		System.out.println(number1 + number2);
}

} [b] main is ending here[/b]

hussey

switch (option) {
	case "A": add();
	case "B" subtract();
}

[B]should be[/B]
switch (option) {
	case 'A': add();
	case 'B' subtract();
}

The double quotes make the input a string since you are using a char it needs to be single quotes

Donny5

Because switch statements don't break after it finds a correct case, you should break after each case.

Also, putting the i/o in the functions isn't great practice, but it doesn't really matter.

I presume you want the Sysouts to print to different lines, in which case, just have the one Sysout and pop in \n for a newline.

Donal

Mimikyu

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Donald-Duck

Loko at your number5 and number6, you made a typo.

By the way, you can re use number1/number2 in all the functions since the variable scope is only within the function

omb0wyn5ehpij9

You have a space in when you are declaring your variables. You either should have no space, or have an underscore.
You should declare your variables as number5 and number6 to stay with the same naming convention you have been using throughout the programme

Mimikyu

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dlofnep

What you can do is use a while loop to take input prior to the switch statement. Use the same variable as the switch statement.

So basically, you would have prior to the switch statement

while(option != 4){ // while the input does not equal 4, then run the switch

// switch case in here

}

Otherwise, it will skip past the switch case and end the program

That way, you will have the menu looping until they select the 4th option. I'd reccommend using numbers over letters for simplicity, as in java you need to use .equals to compare strings instead of == or !=

Best of luck.

Webmonkey

dlofnep wrote: »

What you can do is use a while loop to take input prior to the switch statement. Use the same variable as the switch statement.

So basically, you would have prior to the switch statement

Otherwise, it will skip past the switch case and end the program That way, you will have the menu looping until they select the 4th option. I'd reccommend using numbers over letters for simplicity, as in java you need to use .equals to compare strings instead of == or !=

Best of luck.

Or a do while loop?

dlofnep

Didn't I just say that?

Mimikyu

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Webmonkey

dlofnep wrote: »

Didn't I just say that?

Not really no, plus <snip - i'm half asleep>

do
{
//switch statement in here
} while (option.charAt(0) != 'D');

You are right about numbers though, better choice. Then you can do a range and say wrong option.

Mimikyu

This post has been deleted.

Webmonkey

Since it numbers now and not strings:

do{
switch (option) {
	case 1: add(); break;
	case 2: subtract(); break;
	case 3: multiply(); break;
	case 4: quit(); break;
        default:  //invalid option. Print to screen
           System.out.println("Invalid Choice");

	}
	while (option < 1 && option > 3);

}

Edit - the quit() will have to exit the program or you will get the default case saying invalid choice again.

Mimikyu

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Webmonkey

Oops closing brace wrong place. Half asleep

do{
switch (option) {
	case 1: add(); break;
	case 2: subtract(); break;
	case 3: multiply(); break;
	case 4: quit(); break;
        default:  //invalid option. Print to screen
           System.out.println("Invalid Choice");

	}
}	while (option < 1 && option > 3);

Mimikyu

This post has been deleted.

dlofnep

Webmonkey wrote: »

Not really no, plus <snip - i'm half asleep>

do
{
//switch statement in here
} while (option.charAt(0) != 'D');

You are right about numbers though, better choice. Then you can do a range and say wrong option.

Yeah, do while would probably be cleaner.

Hobbes

Rather then answering all the mistakes for you, it would be better for you to just understand how the error messages work.

So for example

D:\College\Java Programming\Java Programming\Assignment 2\calculator.java:40: while expected
}
 ^

the 40 is the line number in your code where the compiler realised that you have made a mistake and it can't progress.

The ^ character points to the item in the line that is causing the issue. In this case it is just after a bracket.

So you would look for the opening bracket to see what it needed. In this case the error message explains: "while expected". If you trace back to the opening bracket for that then you will see it is "do {". So you need to finish the loop with a while to tell it at what point to exit the loop.

Likewise for the other errors. If the error message doesn't make sense then it is more likely to proceeding line causing the error. In your case the first error is causing all the other errors.

If your code is working but misbehaving then you can use a debugger. That is probably advanced for you. So another option is to put print statements in your code for example.

do{
System.out.println("Entered do. Option was: " + option );
switch (option) {
	case 1: 
             System.out.println("Selected 1. Entering Add");
             add(); 
             System.out.println("Exiting Add");
             break;

So in this example if "Exiting Add" never appeared then you know there is a problem with the line before it.

Once you have finished debugging you can remove the print lines.

Donny5

do{

//put your i/o here

switch (option) {
	case 1: add(); break;
	case 2: subtract(); break;
	case 3: multiply(); break;
	case 4: quit(); break;
        default:  //invalid option. Print to screen
           System.out.println("Invalid Choice");

	}
}	while (option < 1 && option > 3);

Try (option >= 1 && option <= 3).

Webmonkey

Donny5 wrote: »

do{

//put your i/o here

switch (option) {
	case 1: add(); break;
	case 2: subtract(); break;
	case 3: multiply(); break;
	case 4: quit(); break;
        default:  //invalid option. Print to screen
           System.out.println("Invalid Choice");

	}
}	while (option < 1 && option > 3);

Try (option >= 1 && option <= 3).

Correct, got them mixed up lastnight.