missing return statement

[bayan]

Hi guys could you help me out here? I can't tell whats wrong with my code it keeps giving me a missing return statement, } expected.

Heres the class im having problems with.
The program is a calculator in which you type in the expression, which is taken as a string and processed.

public class calculate
{
private String expression;
private double first;
public calculate(String s)
{
expression=s;
first=number();
}
public double number()
{
for(int i=1; i<=expression.length();i++)
{
String num ="";
String temp=expression.substring(i-1,i);
if(temp.compareTo("1")==0 || temp.compareTo("2")==0 || temp.compareTo("3")==0 || temp.compareTo("4")==0 || temp.compareTo("5")==0 ||
temp.compareTo("6")==0 || temp.compareTo("7")==0 || temp.compareTo("8")==0 || temp.compareTo("9")==0 || temp.compareTo(".")==0)
{num+=temp;}
else
{
expression=expression.substring(i);
return Double.parseDouble(num);
}
}
}

public double evaluate()
{
double num1=first;
String operation=expression.substring(0,1);
expression=expression.substring(1);
double num2=number();
if(operation.compareTo("+")==0)
return (num1+num2);
if(operation.compareTo("-")==0)
return (num1-num2);
if(operation.compareTo("*")==0)
return (num1*num2);
if(operation.compareTo("/")==0)
return (num1/num2);
if(operation.compareTo("%")==0)
return (num1%num2);
}
}

No braces missing. Any help appreciated.

[Cemi]

public double number()
{
for(int i=1; i<=expression.length();i++)
{
String num ="";
String temp=expression.substring(i-1,i);
if(temp.compareTo("1")==0 || temp.compareTo("2")==0 || temp.compareTo("3")==0 || temp.compareTo("4")==0 || temp.compareTo("5")==0 ||
temp.compareTo("6")==0 || temp.compareTo("7")==0 || temp.compareTo("8")==0 || temp.compareTo("9")==0 || temp.compareTo(".")==0)
{num+=temp;}
else
{
expression=expression.substring(i);
return Double.parseDouble(num);
}
}
}

Doesn't seem to return anything if the "if" part is true? You have to return a double in both cases. Or is it just me who fail to see it? :)

[m00nchile]

In the evaluate() method, all return statements have an if attached, and none of those ifs have else clauses. What would happen if all ifs return false? Nothing gets returned. Also, even if you construct the if statements to insure at least one of them evaluates to true, the compiler doesn't know that, so even this:

public boolean lessThanZero(int i) {
  if(i < 0)
    return true;
  if(i >= 0)
    return false;
}

would cause a missing return statement error, while this:

public boolean lessThanZero(int i) {
  if(i < 0)
    return true;
  return false;
}

would be fine, since the second return statement occurs if the if statement evals to false.

[bayan]

Hmm im not quite sure how to exit the loop after the first operator is reached.
Maybe recursion works?
Thanks anyway appreciate it :D

[bayan]

Is there any way to force an exit from a loop btw?

[bayan]

Problem solved thanks all for your help :)

-Bayan-

[gcalvin]

By the way, all of your operation.compareTo(<whatever>)==0 logic can be replaced by the simpler operation.equals(<whatever>).

-Gary-