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Questions tagged [bluej]

BlueJ is a popular Java IDE aimed at teaching the principles of object oriented programming.

BlueJ is an open source platform written in Java that's especially aimed at beginner developers. It presents items to the user in a much more easy and intuitive format than more comprehensive IDEs such as Netbeans or Eclipse, helping people get started quickly and easily whilst also understanding what's going on.

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The latest version of BlueJ is available from the download page, here.

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1093 questions
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Using while loops to plot points in java

Hey guys I'm working on an assignment where I have to plot several different points within a range using a while loop to only plot the points while the numbers entered are within the acceptable range. Since I'm doing this for class we're using Bluej…
Scoobert D
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Why is this mutator method returning an error even after calling it?

I have called 'setPrice()' mutator method from a class 'Holiday' which holds 'double' as a data type. However, when I add 'holiday.setPrice()', it says "method setPrice in Holiday class cannot be applied to the given types: double". I am confused to…
Thabo Moyo
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Struggling with string split and regex in Java

in a new BlueJ(java) project I have 4 classes: First some info about my project, I'm following a tutorial task where the main goal is to learn to work with error handling, but I'm not at that part quite yet, I am working with establishing the main…
AnnaM99
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Arrows indicating relationships between classes are missing in BlueJ

Now I am using BlueJ to write some Java programs with my classmate. However, when I get my classmate source code to edit. Some arrows illustrating the relationship between classes are disappeared in my computer. How to fix the problem?
know nothing about programming
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How do i iterate through my ArrayList of objects to create a condition?

I am trying to have my last IF loop to iterate through the three objects within the PinballTypeOne list, only these three objects inside the ArrayList should change their former color to orange once they've hit the left wall. Collision does work,…
Heliangs
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How to call a method from a different class comparing two values?

I am trying to figure out how to call the boolean isAfter(Date compareTo) in my Date class in my Bill class. I keep getting an error message saying "cannot find symbol - method isAfter(Date). I know what I have is not right. Do I have to create a…
Jamie West
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Applying the main function to my bluej project / Making my bluej program a executable .jar

public class Player { // Fields for tracking Class, health and name private String name; private String playerClass; private int health; // Array of classes String[] classes = { …
Peebl
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My BlueJ source code got deleted

I was doing my school project today when suddenly my java BlueJ crashed and both my current file and my backup file got deleted. One of my most important classes(SignIn.java) got deleted(only the source code). While executing, it still works…
Samarth Hari
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JComponents don't appear until mouseover or I minimize the window, and JTextField problems

I'm a 10th Grader from the Philippines, and IT right now is about Java with GUI. Only the basic ones. Our project is to make a POS System. I already made one, but there are some minor problems: JComponents don't appear unless I either minimize the…
Chiba Shinji
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In BlueJ, how do I correctly call variables created in one constructor to a constructor in another class?

I have this code: public class Address { // instance variables private String postcode; private String street; private String town; /** * Constructor for objects of class Address */ public Address(String street, String town, String postcode) { …
D.Harrison
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Why use an ArrayList as a constructor parameter in Java (BlueJ)?

I'm trying to complete an assignment in BlueJ for uni and I've hit a snag at the first hurdle. In the assignment, we are given a class, as well as the names of the constructor, methods, and parameters of that class. We're not allowed to change these…
Prussan
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How would I ask java to stop until a variable is changed?

so I am trying to design a GUI with the program BlueJ, that sends data from a jtextfield box into a variable (already done), and using that variable to be able to update another variable, but for java to "stop running" until a specific variable is…
Michael Merrick
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How do you set the font in BlueJ?

I am currently using BlueJ for programming. Is there a preferences/options menu to change the font to something like Courier? this is kinda trivial, but I couldn't find anything on google.
Registered User
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Adding library in BlueJ

I am wondering if there a way to add Referenced library in blueJ. In eclipse, you can add the referenced library by clicking Build Path>> add external jar. How can you do it in blueJ? It is because I would like to use other library such as…
RedRocket
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Trouble implementing java hangman to return blanks with correct letters (e.g. "_ _ r _")

I've been working on a text-based hangman game in Java BlueJ for a school project and have been mostly successful, but I ran into a bit of a wall with this part. I'm trying to make it so every time the player guesses a letter correctly, it prints…
good people at oracle
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