Thread: Error in IF-Else Code

Hello,
I'm new to java and I am trying to learn it as my first language and eventually move to Programming for Android. To get myself started for practice, I am working on a simple temperature conversion program. It is supposed to Ask the User for "C or F" (Celsius or Fahrenheit) Then if the reply was C, do the conversion, if F, convert to fahrenheit. If the user inputs anything else then give him/her an error. I keep getting errors on the code. First it was on the else code now it is on the if codes. Please help here is the code.

import java.util.Scanner;
import java.io.*;
public class converter {
 
	private static final boolean String = false;
	private static double sum;
 
	public static void main(String args[]) 
	{
 
		Scanner scan = new Scanner(System.in);
	     String usrInput;
 
	     System.out.print("C or F: ");
	     String usrInpt = scan.next();
 
if (String) usrInpt = "C"
{
 
	Scanner temp = new Scanner(System.in);
		System.out.println("Temp: ");
	String celcius = scan.next();
	double n = Double.parseDouble(celcius);
    double sum = ((n * 1.8) + 32);
}
if (String) usrInpt = "F" {
	System.out.println("Working on this");
}
 
else {
	System.out.println("ERROR");
}
 
 
	     System.out.println((double) sum);
	}
}

Ah a but a simple solution, you cannot have two if statements right next to each other, what you have to do for the second if is add a else behind it like:

else if (String) usrInpt = "F" {
System.out.println("Working on this");
}

else {
System.out.println("ERROR");

If you do that the program should work perfectly, also a suggestion, I'm assuming you didn't start with python so beware of your indents in your code cause when you get to more complex stuff, if its not aligned your code will be pretty unreadable not knowing what goes were even if they're curly braces.

Originally Posted by thatguywhoprograms

Ah a but a simple solution, you cannot have two if statements right next to each other, what you have to do for the second if is add a else behind it like:

else if (String) usrInpt = "F" {
System.out.println("Working on this");
}

else {
System.out.println("ERROR");

If you do that the program should work perfectly, also a suggestion, I'm assuming you didn't start with python so beware of your indents in your code cause when you get to more complex stuff, if its not aligned your code will be pretty unreadable not knowing what goes were even if they're curly braces.

What do you mean you can not have two if statements right next to each other?

if(a==b){
}
if(b==c){
}

What's problem in here?


To the OP: The if statement syntax : If StatementStatement ControlJava Tutorial See this.

if (String) usrInpt = "C"

This is an assignment (=) statement not an equality(==) test.
However, You should use the equals() method to compare Strings. The == operator is for primitives.

I done what you said but now I'm getting errors on the if and the else if statements here is my revised code. hat did I do wrong?

if (String) usrInpt = "C" {
 
	Scanner temp = new Scanner(System.in);
		System.out.println("Temp: ");
	String celcius = scan.next();
	double n = Double.parseDouble(celcius);
    double sum = ((n * 1.8) + 32);
}
else if (String) usrInpt = "F" {
	System.out.println("Working on this");
}
 
else {
	System.out.println("ERROR");
}

if (String) usrInpt = "C" {

This is an assignment (=) statement not an equality(==) test.
However, You should use the equals() method to compare Strings. The == operator is for primitives.

I'm getting errors

Copy and post here the full text of the error messages.

Do you mind giving me an example on how to use the equals() method

Here is the full code

import java.util.Scanner;
import java.io.*;
public class converter {
 
	private static final boolean String = false;
	private static double sum;
 
	public static void main(String args[]) 
	{
 
		Scanner scan = new Scanner(System.in);
	     String usrInput;
 
	     System.out.print("C or F: ");
	     String usrInpt = scan.next();
 
if (String) usrInpt = "C" {
 
	Scanner temp = new Scanner(System.in);
		System.out.println("Temp: ");
	String celcius = scan.next();
	double n = Double.parseDouble(celcius);
    double sum = ((n * 1.8) + 32);
}
else if (String) usrInpt = "F" {
	System.out.println("Working on this");
}
 
else {
	System.out.println("ERROR");
}
 
 
	     System.out.println((double) sum);
	}
}

Here is the errors

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
	Syntax error, insert ";" to complete Statement
	Syntax error on token(s), misplaced construct(s)
 
	at converter.main(converter.java:17)

Originally Posted by Norm

Which statement is at line 17?
The compiler is saying that the statement on line 17 needs and ending ;


You need to understand how to read the API doc that describes how to use a class's methods.
Have you read the API doc for the String class? Do you have any questions about its description of the equals() method?
Locate String in lower left and click the link for the doc
Java Platform SE 6

You should also read about how to code an if statement:
The if-then and if-then-else Statements (The Java™ Tutorials > Learning the Java Language > Language Basics)

Sorry for replying so late. At the time of my last post I was away from my computer and was working on my phone through a VNC connection to my computer. Anyways Line 17 is

if (String) usrInpt = "C" {

And I am looking at the docs now, hopefully I can debug this code.

It's not a bug. Its a syntax error.

Isn't a bug usually a programmer error and since this is my error it would be considered a bug?

Ask google or wikipedia.

Originally Posted by Norm

Ask google or wikipedia.

Per Wikipedia,

A software bug is the common term used to describe an error, flaw, mistake, failure, or fault in a computer program or system that produces an incorrect or unexpected result, or causes it to behave in unintended ways. Most bugs arise from mistakes and errors made by people.

Alright I got frustrated and decided to do a complete rewrite. This is what I have so far and it finally compiled and ran successfully.

import java.util.*;
	public class convert {
 
	public static void main(String args[]) {
System.out.println("C or F?: ");
Scanner scan = new Scanner(System.in);
String A = scan.nextLine();
 
if (A.equals("C")) {
		System.out.println("C");
}
else {
	System.out.println("I assume you said F");
}
 
}
}

Instead of assuming, you could test if A was "F" and if not, print out an error message.

Well I was up till 1 last night trying to get it working and I think I finally did. It will ask for "C or F" Then if C or F is entered it will ask for the temperature and then do the conversion and loop back to the beginning. If anything but C or F was entered then it throws an error.

import java.util.*;
	public class convert {
 
	public static void main(String args[]) {
 
		dothis();
	}
	public static void dothis(){
		System.out.println("");
System.out.println("C or F?: ");
Scanner scan = new Scanner(System.in);
String A = scan.nextLine();
 
if (A.equals("C")) {
	System.out.println("What is the temperature in Celcius: ");
	Scanner cel = new Scanner(System.in);
	double B = Double.parseDouble(cel.nextLine());
	double ans = ((B * 9/5) + 32);
	System.out.print((double) ans);
	dothis();
} else if (A.equals("F")){
	System.out.println("What is the temperature in Farenheit: ");
	Scanner fa = new Scanner(System.in);
	double F = Double.parseDouble(fa.nextLine());
	double Fans = ((F - 32) * 5/9 );
	System.out.print((double) Fans);
	dothis();
}
else {
	System.out.println("ERROR");
}
	}
 
 
 
 
 
}

if(usrInpt.equals("C")) {

You need to have parenthesis to surround the if statement.

Originally Posted by imsuperman05

if(usrInpt.equals("C")) {

You need to have parenthesis to surround the if statement.

What do you mean? The program runs without error so if I may ask, can I see an example and what will the parenthesis do? I don't mean to sound like a know-it-all, I'm just wondering why I performed an error

Originally Posted by jonathon6017

What do you mean? The program runs without error so if I may ask, can I see an example and what will the parenthesis do? I don't mean to sound like a know-it-all, I'm just wondering why I performed an error

Do you even compile the file? It should show errors.

Originally Posted by imsuperman05

Do you even compile the file? It should show errors.

The exact code I posted above is what I compiled and ran and it ran with no errors

The line should have been
if(usrInpt=="c")

Originally Posted by copeg

FYI Never, unless you have reason to compare objects, use == to compare strings. String's are objects, and thus should be compared using the equals method

Sorry, the above reply of mine was made seeing the last reply on page 1 of this thread.
But, I always use == to compare a variable(referring to a String) with a string constant in decision making statements. What's wrong with it?

What's wrong with it?

The == operator tests if the two references point/refer to the same object.
It is possible for there to be two Strings (ie two different objects) with the same contents. The equals method would say they had the same value (true), the == operator would say the references point to different objects (false).