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Java : while loop not detecting break condition but if block does

just want to break out of this while loop. Condition doesn't break when I assumed it will, but it does get registered by the subsequent if statement.
String current_Class_Name = "";
int current_Class_Rating;
while(!current_Class_Name.equals("Done")) {
// * Get class name.
System.out.println("What class are you rating?");
current_Class_Name = in.nextLine();
// *
// if(current_Class_Name.equals("Done")) {
// System.out.println("Detected 'Done'");
// break;
// }
// * Get class rating.
System.out.println("How many plus signs does " + current_Class_Name + " get?");
current_Class_Rating = Integer.parseInt(in.nextLine());
// * If user inputs an invalid rating (not a value between 0-5),
// * keep prompting them until they enter a valid input.
while(current_Class_Rating > 5 || current_Class_Rating < 0) {
System.out.println("Sorry, but you can only give a rating of 0-5.");
System.out.println("How many plus signs does " + current_Class_Name + " get?");
current_Class_Rating = Integer.parseInt(in.nextLine());
}
// * TODO
// * Add to STRING and INTEGER LISTS.
}
Possibly some kind of call order problem as the String is "empty" upon entering the while loop.
Sorry for any formatting.
Thanks for any and all help.
NOTE : I typically use C# and as far as I remember, a while loop will try and detect the condition case before completing an entire iteration.
EDIT : The if statement is not there to run, but to just prove two things : 1) that the break condition can be detected and 2) to break out at a given time.
EDIT : Updated to show all code in consideration.

Try changing the implementation to:
String current_Class_Name = null;
Integer current_Class_Rating = null;
do {
// * Get class name.
System.out.println("What class are you rating?");
current_Class_Name = in.nextLine().trim();
try {
// * Get class rating.
System.out.println(String.format("How many plus signs does '%s' get?",current_Class_Name));
current_Class_Rating = Integer.parseInt(in.nextLine().trim());
}catch(NumberFormatException e) {
current_Class_Rating = null;
}
if((current_Class_Rating == null)||(!(current_Class_Rating>=0 && current_Class_Rating <=5))) {
System.out.println("Invalid rating value! Rating must be integer 0-5!");
continue; // skips back to beginning of the loop
}
// * TODO
// * Add to STRING and INTEGER LISTS.
}while(!current_Class_Name.equalsIgnoreCase("done"));

Your question appears to have been based on a misconception, the while loop will only terminate when the condition is re-evaluated to be false at the top (not on the instant of the variable being updated). However, you can make it so the prompt, the assignment and the evaluation happen at once. First, create a helper method. Like,
private static String promptForClassName(Scanner in) {
System.out.println("What class are you rating?");
return in.nextLine();
}
Then, use it with the fact that assignment (as a side-effect) evaluates to the assigned value; also, please follow standard Java camel case naming conventions. Like,
String currentClassName;
while (!(currentClassName = promptForClassName(in)).equalsIgnoreCase("Done")) {
String prompt = "How many plus signs does " + currentClassName + " get?";
// * Get class rating.
System.out.println(prompt);
int currentClassRating = Integer.parseInt(in.nextLine());
// * If user inputs an invalid rating (not a value between 0-5),
// * keep prompting them until they enter a valid input.
while (currentClassRating > 5 || currentClassRating < 0) {
System.out.println("Sorry, but you can only give a rating of 0-5.");
System.out.println(prompt);
currentClassRating = Integer.parseInt(in.nextLine());
}
// * TODO
// * Add to STRING and INTEGER LISTS.
}
System.out.println("Detected 'Done'");

Guessing Game Help :)

Ok, so my computer teacher has asked us to make a simple game that asks the user to guess a radomly generated number, but I want to take it one step further and make it so that it display error messages when the user tries certain things. The problem here is that I am new to booleans and well, I am having a bit of trouble using java.util.Scanner and booleans. So, if anyone could take a quick look at this I would appreciate it.
import java.util.Scanner;
import java.util.Random;
public class MoreGuessing{
//Instantiation
Scanner reader = new Scanner(System.in);
Random number = new Random();
//Variables
int randomnumber = number.nextInt(10) + 1;
int cntr = 1;
static String decimalguessed;
String error1 = "Error001: Decimal found, please enter a whole number between 1-10." + "\n" + "Program terminated......";//Decimal portion error.
String error2 = "Please enter a positive number." + "\n" + "Program terminated......"; //Negative number error.
String error3 = "Unknown character entered." + "\n" + "Program terminated......"; //Unknown character error.
//Verifier
public static boolean verifyLetters() {
if (decimalguessed.matches("[a-zA-Z]+")){
return true;
}else{
return false;
}
}
public static void main(String [] args){
//Input and display
System.out.print("Please enter a whole number between 1-10: ");
decimalguessed = reader.nextLine();
//Process and Errors
while (decimalguessed != randomnumber) {
if (verifyLetters() != false){
System.out.println(error3);
System.exit(1);}
if (decimalguessed % 1 != 0) {
System.out.println(error1);
System.exit(1);}
if (decimalguessed < 0) {
System.out.println(error2);
System.exit(1);}
if (randomnumber != decimalguessed){
System.out.println("You've lost, please make another attempt.");}
System.out.print("Please enter a whole number between 1-10: ");
decimalguessed = reader.nextDouble();
cntr++;
}
if (cntr == 1) {System.out.println("Congratulations! You've guessed the number on your first attempt!");;
}
else {System.out.println("Congratulations! You've guessed the number, it took you " + cntr + " tries");}
}
}

You need to parse your input. decimalguessed is a string, and so you can't do comparisons like decimalguessed % 1.
You can convert it to an integer like this:
int guess = 0;
try {
guess = Integer.parseInt(decimalguessed);
} catch (NumberFormatException e) {
System.out.println("Your guess was not an integer: " + e.getMessage());
System.exit(1);
}
This will handle both cases where decimalguessed contains letters, and where it contains decimal points/fractions. decimalguessed is still a string, but guess now contains the integer version of it, so you can compare it to randomnumber properly. (Your loop would have never exited before, because a string is never == an integer)
Some other notes:
You should never have:
if (condition) {
return true;
} else {
return false;
}
This can always be simply replaced with
return condition;

It feels like you're very new to this. Welcome to programming!
So first, in Java generally you're not going to have all of that instantiation and variables stuff outside of your main function, unless you're going to make everything static. I would move all of that into your main function, un-static the decimalguessed variable and setup your verifyLetters function to take an argument of String decimalguessed. It may also be wise to check if the value is a number, rather than seeing if it is not a letter. There a lot of non-number, non-letter characters.
Once you've figured out that the guess is a number, you need to tell java it is one (cast it) to a decimal, then do you further comparisons against that decimal.
Darth Android also makes some good points, especially about booleans. You should never have the only result of an if/else be to return a boolean, just return the boolean. Also avoid comparisons to true/false, just do the if on the function/variable alone, or negate it with an '!' to check for false.
Good luck!

How to read String and input from a single line of input from scanner

Language: Java.
Aim:
Boolean Array gridA[] should become true on whatever index is read from input (i.e. if input is "init_start 2 4 5 init_end" then gridA[] indexes 2,4 and 5 should become true). That much I managed to get working but I have two problems:
input:
init_start int int int int int (...) int init_end
for example: init_start 2 6 12 init_end
Problems:
any integer from input that exceeds the value of (instance variable) int L (which determines the index-length of the array) should be ignored, to prevent integers from outside the domain of Array gridA[] from having influence.
Using if(scanner.nextInt != L){} didn't seem to work.
I also need this method, or the body of the method to start when input begins with "init_start" and stop when input ends with "init_end".
How do write code so that it can read both String and integers from the same input?
I meant to do this using
if(scanner.Next=="init_start") followed by
a = scanner.NextInt; which, as I suspected, didn't work.
Attempts at solving:
After googling I tried putting String initialInputStart in a Scanner:
localScanner(initialInputStart);
but I failed to get that working. Other information I found suggested I'd close and reopen the scanner but I need the information to be read from a single line of input so I doubt that will help.
code:
java.util.Arrays.fill(gridA,false);
java.util.Arrays.fill(gridB,false);
String initialInput;
String initialInputStart;
int a;
int i;//only for testing
i = 0;//only for testing
System.out.println("type integers"); //only for testing
while( scanner.hasNextInt() && i<5){ //I can't find a way to make loop stop without missing input so I'm using i temporarily
a = scanner.nextInt();
gridA[a] = true;
System.out.print(a);
System.out.print(gridA[a]+" ");
i++;
}//end while

I wrote a little program which pretty much does what you described as your aim; I read line by line and split each into tokens I further process. The tokens describe what the data means/what state we are in. The actual data is parsed in the default: case in the switch(token) block and branches in behaviour from state to state (which is merely visible here as we only have two states: "init" and "not init", beside the keywords):
public static void main(String[] args) {
int L = 13; // not sure if this is needed
boolean[] gridA = new boolean[L];
Reader source;
/**
* from file:
* source = new FileReader("grid.csv");
*/
/**
* from classpath resource:
* source = new InputStreamReader(MyClass.class.getResourceAsStream("grid.csv"));
*/
/**
* from string:
* source = new StringReader("init_start 2 6 12 init_end");
*/
/**
* from std-in:
* source = new InputStreamReader(System.in);
*/
try(BufferedReader stream = new BufferedReader(source)) {
boolean init = false;
// loop
input_loop:
while(true) {
// read next line
String line = stream.readLine();
if(line == null) {
// end of stream reached
break;
}
if(line.trim().isEmpty()) {
// ignore empty lines
continue;
}
String[] tokens = line.split(" ");
for (String token : tokens) {
switch (token) {
// evaluate keywords
case "init_start":
init = true;
break;
case "init_end":
init = false;
break;
// for input from console
case "exit":
break input_loop;
default:
// parse input, based on state (expand "init" to an enum for more states)
if(init) {
// read init input
int index = Integer.parseInt(token);
if(index >= 0 && index < gridA.length) {
gridA[index] = true;
} else {
throw new RuntimeException("illegal grid index: " + index);
}
} else {
// read undefined input
throw new RuntimeException("unrecognized token: " + token);
}
break;
}
}
}
} catch(IOException ex) {
throw new RuntimeException("an i/o exception has occurred", ex);
}
System.out.println(Arrays.toString(gridA));
}

" How do write code so that it can read both String and integers from the same input?"
do you want to have an Input like this: "123, foo"
if thats the case use:
String input = scanner.nextLine();
String[] parts = input.split(",");//" " to split it at an empty space
String part1 = parts[0]; // 123
int Number = Integer.parseInt(part1) // you could inline it, but i chose this version for better refference
String part2 = parts[1]; //foo
if your Input looks like this "123 or foo"
you have to read the input as String and check the String afterwards if its a Number:
String input = scanner.nextLine();
if (text.contains("[a-zA-Z]+") == false){ //looks if the input does NOT contain any characters
int nummber = Integer.parseInt(input);
} else{
String text = input;
}
afterward you can compare your text:
For the first mentioned case:
if("init_start".equals(parts[1])){ //*
yourMethod();
}
For the other case:
if("init_start".equals(text)){ //*
yourMethod();
}
*Also:
"I meant to do this using if(scanner.Next=="init_start")"
*Very important! To compare Objects, such as String use .equals(). "==" only works on primitive types
Edit: I've read your example. You could go with a combination of my solutions. split the string at space(" ") and check parts[x] if it is an integer. But i wouldnt recommend this method! Why dont you split your input in three parts: init_start would start your function. After that your method would expect an input of Integers like "int int int" after you inserted the Integers your function could automatically stop or wait for the input "init_stop". That seems to me more reasonable. If you want to go with the single line solution you can evaluate the number of your int's by get tingparts[].lenght()-2

use this implementation:
public static void main(String args[]){
try{
Scanner in = new Scanner(System.in);
System.out.println("Enter a line");
String dat = in.readLine();
System.out.println(dat);
}
catch(IOException e){
System.out.println("IO ERROR !!!");
System.exit(-1);
}
}

What is the format of calling a method from another class?

If I would like to call a method from another class to input it into the current class that I am working on, how do I format it to call the method? How is the code written to call for the method. Currently I have my floats array that is a method? written in another class and I would like to call for the function to be inputed into the class that I am working on. I honestly don't mean to sound ignorant but I am having hard tie trying to grasp how java works. Thanks.
This is what i put. The float array and the name = the name of the class? I am pretty sure it is incorrect because I am getting an error that myPickNumbers cannot be resolved.
float[] myFloats = myPickNumbers.pickNumbers();
I am trying to take this:
import java.util.InputMismatchException;
import java.util.Scanner;
public class pickNumbers {
Scanner readInput = new Scanner(System.in);
float [] pickNumbers(int choice){
float []myFloats = new float[2];
do { //do loop will continue until user enters correct response
System.out.print("Please enter 2 numbers separated by a space in the formats of floats: "); //will prompt user to enter 2 floats
try {
myFloats[0] = readInput.nextFloat(); //will read first float entered
myFloats[1] = readInput.nextFloat(); //will read second float entered
if (choice == 4 && myFloats[1] == 0.0f) {
System.out.println("Cannot complete calculation. Cannot divide by 0, please try again.");
myFloats[0] = myFloats[1] = 0.0f;
continue;
}
break;
} catch (final InputMismatchException e) {
System.out.println("You have entered an invalid input. Try again.");
readInput.nextLine(); // discard input that is not a float
continue; // loop will continue until the correct answer is found
}
} while (true);
return myFloats;
}
}
And put it into this:
public class Calculator {
public static void main(String[] args) {
String inputOperation;
String operatingWord[] = { "adding", "subtracting",
"multiplying", "dividing" };
//array of operations to display to user
Selection mySelection = new Selection();
String menu = "Welcome to John Doe's Calculator" //next line print out line for welcome
+ "\n 1. Addition"//next line option 1 for addition
+ "\n 2. Subtraction" //next line option 2 for subtraction
+ "\n 3. Multiplication" //next line option 3 for multiplication
+ "\n 4. Division" //next line option 4 for division
+ "\n 5. Exit\n"
+ "====================================\n\n"; //next line option 5 for exit then leave a blank line
Symbol.newSymbol(menu);
Symbol.displaySymbol();
while (!(inputOperation = mySelection.selectionOne()).equals("5"))
Symbol.newSymbol("\n");
Symbol.displaySymbol();
float[] myFloats = myPickNumbers.pickNumbers();

You are trying to use a variable, myPickNumbers that you neither declare nor initialize. You must first declare it and initialize it before you can use it:
pickNumbers myPickNumbers = new pickNumbers();

You should first declare a new pickNumbers object
pickNumbers myPickNumbers = new pickNumbers();
Then you can call the pickNumbers() method but you have to include a parameter of type int e.g
float[] myFloats = myPickNumbers.pickNumbers(5)

Continually Validating Integers

I have a method I'm using to validate user-inputted values in a program. Whenever the user inputs a string into a JOptionPane, I call this method and pass in the inputted string, plus the maximum and minimum values I need their input to be between. First I check if the input is an integer by trying to parse the input string and catching exceptions, then I check if the integer is between the min and max. My problem is that if the user inputs another incorrect non-integer value after being prompted, I don't know how to check if the new value is correct or not. Here is the method, can anybody help?
int checkInput(String input, int min, int max) {
Boolean isInteger = false;
Boolean inputAccepted = false;
int userInput = 0; //will be set later
while (!isInteger) {
try
{
userInput = Integer.parseInt(input);
}
catch (NumberFormatException e)
{
userInput = Integer.parseInt(JOptionPane.showInputDialog("Please enter only integers between " + min + " and "+ max + "."));
isInteger = true; //the problem here is that it assumes the user inputted a correct value after being prompted... what if they enter another incorrect value?
}
}
while (!inputAccepted) {
if (userInput < min || userInput > max)
{
userInput = Integer.parseInt(JOptionPane.showInputDialog("Please enter only integers between " + min + " and "+ max + "."));
}
else
{
inputAccepted = true;
}
}
return userInput;
}

I believe the main problem is that you have a method whose job isn't simple and well-defined. It looks like you have a statement outside this method that inputs a number; but checkInput has two jobs: making sure the number is valid, and inputting more numbers until it is. This is a problem in two ways: your code that does the input is duplicated in two places, and you have a method whose responsibility isn't clear.
Instead, try writing a method that just checks whether the input is valid, and returns true or false. I'd change the name to isValidInput. The caller would then have a loop that would perform the input, make sure it's valid, and go back if it isn't.
Usually I wouldn't answer a question like this by pointing to flaws in your design. But I think that in this case, if you rethink your design, your question will answer itself. (That's often the case when you design things correctly--things fall into place.)

Your checkInput() function should throw its own exception if the input is not correct. Spliting the code into a validator and a parser would result in parsing the input twice.