Please help a beginner java programmer!

[Hazza]

Hello,
I am teaching myself java and am completely stuck. I am using the java development kit and vista command prompt to compile and interpret programmes. I am getting error codes which don't make sense because they refer to a code that seems all right to me. Here is the code:
[CODE=java]
class calculator {
public static void main(String[] arguments) {
float numbera = 100;
float numberb = 200;

if (arguments.leng th > 0) {
numbera = Float.parseFloa t(arguments[0]);
sign = Char.parseChar (arguments[1]);
numberb = Float.parseFloa t(arguments[2]);
}

if (sign == +)


System.out.prin tln(numbera
+ "added to "
+ numberb
+ " is "
+ (numbera + numberb));

if (sign == -)


System.out.prin tln(numbera
+ "subtract "
+ numberb
+ " is "
+ (numbera - numberb));

if (sign == *)


System.out.prin tln(numbera
+ "multiplied by "
+ numberb
+ " is "
+ (numbera * numberb));

if (sign == /)


System.out.prin tln(numbera
+ "divided by "
+ numberb
+ " is "
+ (numbera / numberb));

}
}

[/CODE]

I am getting 6 error codes, all saying "illegal start of expression". They are at:

The last bracket of [CODE=java] if (sign == +) [/CODE]
The last bracket of [CODE=java] if (sign == -) [/CODE]
The multiplication sign of [CODE=java] if (sign == *) [/CODE]
The last bracket of [CODE=java] if (sign == *) [/CODE]
The division sign of [CODE=java] if (sign == /) [/CODE]
The last bracket of [CODE=java] if (sign == /) [/CODE]

I have been trying for a long time to find a solution but to no avail. Please could someone help me?.
Thank you

[Ganon11]

The +, -, *, and / characters alone are arithmetic operators. If you want to compare sign to the characters, use '+', '-', '*', or '/', which are the characters, not the operators.

[Hazza]

I realised that I should have used if else statements. Here is the revised code
[CODE=java]
class calculator {
public static void main(String[] arguments) {
float numbera = 100;
float numberb = 200;

if (arguments.leng th > 0) {
numbera = Float.parseFloa t(arguments[0]);
sign = Char.parseChar (arguments[1]);
numberb = Float.parseFloa t(arguments[2]);
}



if (sign == +) {


System.out.prin tln(numbera
+ "added to "
+ numberb
+ " is "
+ (numbera + numberb));}

else if (sign == -){


System.out.prin tln(numbera
+ "subtract "
+ numberb
+ " is "
+ (numbera - numberb));}

else if (sign == *){


System.out.prin tln(numbera
+ "multiplied by "
+ numberb
+ " is "
+ (numbera * numberb));}

else if (sign == /){


System.out.prin tln(numbera
+ "divided by "
+ numberb
+ " is "
+ (numbera / numberb));}

}
}

[/CODE]

I am still getting six error messages for "illegal start of expression at for the last bracket ( this type of bracket )) of the if ( concerning addition) statement,the last bracket ( this type of bracket )) of the first else if ( concerning subtraction) statement,the last bracket ( this type of bracket )) and multiplication sign (*) of the second else if ( concerning multiplication) statement, and the last bracket ( this type of bracket )) and division sign of the last else if ( concerning division) statement,
When I say last bracket (of this type)) I meant on the line with the statement,
if (sign == +) {,
not after the rest of it. Thank you in advance to anyone who helps

[Hazza]

It still doesn't work

Sorry Ganon I posted the second thing before I saw your reply. here is the code i am now using [CODE=java]

class calculator {
public static void main(String[] arguments) {
float numbera = 100;
float numberb = 200;

if (arguments.leng th > 0) {
numbera = Float.parseFloa t(arguments[0]);
sign = Char.parseChar (arguments[1]);
numberb = Float.parseFloa t(arguments[2]);
}



if (sign == '+')


System.out.prin tln(numbera
+ "added to "
+ numberb
+ " is "
+ (numbera + numberb));

else if (sign == '-')


System.out.prin tln(numbera
+ "subtract "
+ numberb
+ " is "
+ (numbera - numberb));

else if (sign == '*')


System.out.prin tln(numbera
+ "multiplied by "
+ numberb
+ " is "
+ (numbera * numberb));

else if (sign == '/')


System.out.prin tln(numbera
+ "divided by "
+ numberb
+ " is "
+ (numbera / numberb));

}
}


[/CODE]
now the errors i am getting are 6 cannot find symbol errors.
(
cannot find symbol
symbol : variable (depends)
location: class calculator
They look like this.
1. Its the sign in the

 sign = Char.parseChar (arguments[1]);

statement
2. The first Char in the

 sign = Char.parseChar (arguments[1]);

statement
3. And all the signs in the if and else if statements (example

 else if (sign == '-')

[Hazza]

I got rid of all but one of the errors by declaring the "sign" variable at the beginning as a char variable so the first few lines look like this:
[CODE=java]

class calculator {
public static void main(String[] arguments) {
float numbera = 100;
float numberb = 200;
char sign = '+';
[/CODE]

I also changed Char to Character.parse Char
The only error that remains is;
Cannot find symbol
Symbol = method parseChar(java. lang.String)
location = class java.lang.Strin g)
sign = Character.parse Char (arguments[1]);
with the little hat under the full stop in the last line (vista comman prompt)
Thanks in advance

[Ganon11]

If you know that arguments[1] has the sign, why not use the .charAt() function to grab the first character of that String? This function returns a character, so there's no need to use parseChar.

[JosAH]

If you know that arguments[1] has the sign, why not use the .charAt() function to grab the first character of that String? This function returns a character, so there's no need to use parseChar.

... or alternatively make variable sign a String and do this:

[code=java]
String sign= arguments[1];

if (sign.equals("+ ")) { ... }
if (sign.equals("-")) { ... }
if (sign.equals("* ")) { ... }
if (sign.equals("/")) { ... }
[/code]

kind regards,

Jos

[Hazza]

Thanks Ganon - now everything works except multiplication.
I am mystified to why this is, because the code is exactly the same to the other mathematical functions.
Here is my full code [CODE]

class calculator {
public static void main(String[] arguments) {
float numbera = 100;
float numberb = 200;
char sign = '*';

numbera = Float.parseFloa t(arguments[0]);
sign = arguments[1].charAt(0);
numberb = Float.parseFloa t(arguments[2]);





if (sign == '+') {


System.out.prin tln(numbera
+ " added to "
+ numberb
+ " is "
+ (numbera + numberb));}

else if (sign == '-'){


System.out.prin tln(numbera
+ " subtract "
+ numberb
+ " is "
+ (numbera - numberb));}

else if (sign == '*'){


System.out.prin tln(numbera
+ " multiplied by "
+ numberb
+ " is "
+ (numbera * numberb));}


else if (sign == '/'){


System.out.prin tln(numbera
+ " divided by "
+ numberb
+ " is "
+ (numbera / numberb));}

}
}

[CODE]

I can type in java calculator 6 + 8 or 8 / 5 or 78 - 5 but not anything with a multiplication sign in it like 8 * 7.
The error message looks like this.
Exception in thread "main" java.lang.Numbe rFormatExceptin : For input string "addition.j ava"
at sun.misc.Floati ngDecimal.readJ avaFormatString (Unknown Source)
at java.lang.Float .parseFloat(Unk nown source)
at calculator.main (test.java:10)

It says "addtion.ja va" in the error message, and I do have a file in the folder of this progrm, but there is no reference to either to either program. In case it should help, here is the code for it, which is a prototype for calculator:
[CODE]
class addition {
public static void main(String[] arguments) {
float numbera = 100;
float numberb = 200;
if (arguments.leng th > 0) {
numbera = Float.parseFloa t(arguments[0]);
numberb = Float.parseFloa t(arguments[1]);

}
System.out.prin tln(numbera
+ " added to "
+ numberb
+ " is "
+ (numbera + numberb) );
}
}
[CODE]
Thanks

[JosAH]

Thanks Ganon - now everything works except multiplication.
I am mystified to why this is, because the code is exactly the same to the other mathematical functions.

<code snipped>

I can type in java calculator 6 + 8 or 8 / 5 or 78 - 5 but not anything with a multiplication sign in it like 8 * 7.
The error message looks like this.
Exception in thread "main" java.lang.Numbe rFormatExceptin : For input string "addition.j ava"
at sun.misc.Floati ngDecimal.readJ avaFormatString (Unknown Source)

Add the following statement at the beginning of your main method and you'll
see why a single '*' on the command line won't work as you expected:

[code=java]
for (int i= 0; i < argument.length ; i++)
System.out.prin tln("argument["+i"]="+argument[i]);
[/code]

kind regards,

Jos

[Hazza]

Sorry, I don't quite understand - where do i put that statement in my code and what does it do?

If i put your code directly after the public static void main(String[] arguments) {
I get 3 error messages saying that there is a ; expected (with the hat under the last ) of your code), that it is not a statement with the hat under the last put one square bracket, and that a normal bracket is expected, with the hat under the thrid ".
Thanks for your help

[JosAH]

Sorry, I don't quite understand - where do i put that statement in my code and what does it do?

If i put your code directly after the public static void main(String[] arguments) {
I get 3 error messages saying that there is a ; expected (with the hat under the last ) of your code), that it is not a statement with the hat under the last put one square bracket, and that a normal bracket is expected, with the hat under the thrid ".
Thanks for your help

Do this:

[code=java]
public static void main(String[] argument) {
for (int i= 0; i < argument.length ; i++)
System.out.prin tln("argument["+i"]="+argument[i]);

// your code goes here
// ...
[/code]

kind regards,

Jos

[Hazza]

I did that and got the same error messages.

Here is my complete code (with yours included)
[CODE]

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


for (int i= 0; i < argument.length ; i++)
System.out.prin tln("argument["+i"]="+argument[i]);



float numbera = 100;
float numberb = 200;
char sign = '+';

numbera = Float.parseFloa t(arguments[0]);
sign = arguments[1].charAt(0);
numberb = Float.parseFloa t(arguments[2]);

if (sign == '+') {


System.out.prin tln(numbera
+ " added to "
+ numberb
+ " is "
+ (numbera + numberb));}

else if (sign == '-'){


System.out.prin tln(numbera
+ " subtract "
+ numberb
+ " is "
+ (numbera - numberb));}

else if (sign == '*'){



System.out.prin tln(numbera
+ " multiplied by "
+ numberb
+ " is "
+ (numbera * numberb));}


else if (sign == '/'){


System.out.prin tln(numbera
+ " divided by "
+ numberb
+ " is "
+ (numbera / numberb));}

}
}

[CODE]
Thanks for your help

[JosAH]

I did that and got the same error messages.

Here is my complete code (with yours included)
[CODE=java]
public static void main(String[] arguments) {


for (int i= 0; i < argument.length ; i++)
System.out.prin tln("argument["+i"]="+argument[i]);
[/CODE]
Thanks for your help

Duh, my mistake: you named your command line arguments 'arguments', not
'argument' as I did; make that code snippet like this:

[code=java]
public static void main(String[] arguments) {


for (int i= 0; i < arguments.lengt h; i++)
System.out.prin tln("arguments["+i"]="+arguments[i]);
[/CODE]

kind regards,

Jos

[Hazza]

i updated my code and i am still getting the same error messages
thanks

[JosAH]

i updated my code and i am still getting the same error messages
thanks

Found it; silly me: I should be just lazy on a Sunday morning; not posting wrong
code; change that println statement to this:

[code=java]
System.out.prin tln("arguments["+i+"]="+arguments[i]);
[/code]

Note that extra '+' sign I forgot in the previous (incorrect) versions.

kind regards,

Jos