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| − | ==Introduction==
| + | {{1010Topic}} |
| − | The while loop is a special form of [[Loops|loop]] that will continue to repeat as long as the [[test condition]] evaluates to ''true''.
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| − | | + | |
| − | ==Syntax==
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| − | In java, the while loop takes the form of
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| − | <pre>
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| − | while(test condition)
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| − | { | + | |
| − | ...
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| − | statements
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| − | ...
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| − | }
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| − | </pre>
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| − | In this particular situation, the while loop will continue to iterate as long as the test condition evaluates to true
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| − | | + | |
| − | ==Uses==
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| − | A while loop is useful in any situation where you don't know beforehand how often you want to repeat the block of code. Consider the following situation instance:
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| − | <pre>
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| − | import javax.swing.JOptionPane;
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| − | public class Input
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| − | { | + | |
| − | public static void main(String args[])
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| − | {
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| − | String done;
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| − | done = JOptionPane.showInputDialog("Enter a phrase, type quit to finish");
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| − |
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| − | while(!done.equals("quit"))
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| − | {
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| − | System.out.println("Hello " + name);
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| − | done = JOptionPane.showInputDialog("Enter a phrase, type quit to finish");
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| − | }
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| − | }
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| − | }
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| − | </pre>
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| − | This code will repeatedly ask the user for input, and display that input, until the user types quit.
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| − | | + | |
| − | ==Assignments==
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| − | Ignore the //<--Comment--> comments until you've read the assignment modification at the bottom
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| − | '''Asst. 1'''
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| − | Guess my number program
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| − | <pre>
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| − | import javax.swing.JOptionPane;
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| − | public class GuessNumber
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| − | {
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| − | public static void main(String args[])
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| − | {
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| − | int myNumber = 29;
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| − | String number;
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| − | int guess;
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| − | //<--Min and max variables go here-->
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| − | | + | |
| − | //get guess from user
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| − | number = JOptionPane.showInputDialog("Pick a number between 1 and 100"); //<--Show user min and max-->
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| − | | + | |
| − | //convert number from string to integer
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| − | guess = Integer.parseInt(number);
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| − | while(guess != myNumber) {
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| − | if(guess < myNumber)
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| − | {
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| − | //<--Modify min or max variables here-->
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| − | number = JOptionPane.showInputDialog("Too low, please try again); //<--Show user min and max-->
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| − | }
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| − | else
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| − | {
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| − | //<--Modify min or max variables here-->
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| − | number = JOptionPane.showInputDialog("Too high, please try again); //<--Show user min and max-->
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| − | }
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| − | //convert number from string to integer
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| − | guess = Integer.parseInt(number);
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| − | }
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| − | JOptionPane.showMessageDialog(null, "Congratulations, you picked the right number");
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| − | }
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| − | }
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| − | </pre>
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| − | This program will ask the user to guess the number until the user guesses correctly. How can this program be improved?
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| − | Modify this program so that the program tells the user whether they guessed too high or too low. Hints have been placed in the program in comments.
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| − | [[While_Loops_Answers_1|Answer]]
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| − | '''Asst. 2'''
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| − | Pick up stones
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| − | '''Note:''' May want to read up on [[test condition#Logical Operators|Logical Operators]] before doing this one.
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| − | <pre>
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| − | import javax.swing.JOptionPane;
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| − | | + | |
| − | public class Stones
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| − | {
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| − | public static void main(String args[])
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| − | {
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| − | int totalStones = 21;
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| − | | + | |
| − | String number;
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| − | int removed;
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| − | //<--Uncomment when doing assignment-->
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| − | //JOptionPane.showMessageDialog(null, "Pick up 1-3 stones until all are gone");
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| − | | + | |
| − | //get guess from user
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| − | number = JOptionPane.showInputDialog("There are " + totalStones + " stones, pick up how many?");
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| − | | + | |
| − | //convert number from string to integer
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| − | removed= Integer.parseInt(number);
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| − | | + | |
| − | //<--Ask the user for another input while removed > 3 or removed <= 0 or removed > totalStones-->
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| − |
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| − | //remove stones from pile
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| − | totalStones -= removed;
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| − | while(totalStones > 0) {
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| − | number = JOptionPane.showInputDialog("There are " + totalStones + " stones, pick up how many?");
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| − | | + | |
| − | //convert number from string to integer
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| − | removed= Integer.parseInt(number);
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| − | | + | |
| − | //<--Ask the user for another input while removed > 3 or removed <= 0 or removed > totalStones-->
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| − |
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| − | //remove stones from pile
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| − | totalStones -= removed;
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| − | }
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| − | JOptionPane.showMessageDialog(null, "All the stones are gone");
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| − | }
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| − | } | + | |
| − | </pre>
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| − | This program allows the user to remove stones, as many as they want, until there are no stones remaining.
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| − | Modify this program so that the user cannot remove more than 3 stones at a time, and so that the user cannot remove more stones than there are available.
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| − | [[While_Loops_Answers_2|Answer]]
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| − | | + | |
| − | '''[[Loops|Back to Loops]]'''
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