I want to use the StdDraw package, and I've tried many different ways of importing it.
Of course I tried:
import StdDraw;
But, when I look at the documentation from Princeton here, it shows that StdDraw is part of Objects, so I try this:
import java.lang.Object.StdDraw;
However, this results in an error:
error: cannot find symbol in
import java.lang.Object.StdDraw;
I saw this question here but it does not answer this question either.
How do I import StdDraw? thank you.
if you want to use StdDraw you must have
either the sources
or the classes (best zipped up as jar)
as preferred way you use the sources (see http://introcs.cs.princeton.edu/java/15inout/). it says there "To use these libraries, download StdIn.java, StdOut.java, StdDraw.java, and StdAudio.java into the same directory as your program. "
once you did this the imports should be working.
NOTE: all four files are not in packages, so you should 'download' them into the 'standard' package. That means you have to download them to the root package of your project.
by the way: don't import import java.lang.Object.StdDraw; but do just import import StdDraw;
First of all check encoding of your IDE. It should be set to UTF-8. It is important if you are using MS Windows operating system.
Then create StdDraw.java class in the same package as the package of your program you are writing. Remove class declaration, leave only package declaration.
Then visit this page: https://introcs.cs.princeton.edu/java/stdlib/StdDraw.java .
Copy all its contents (Ctr-A, Ctrl-C) and then paste it into StdDraw.java file you created previously.
StdDraw.java has its own main method so try to run it in order to check that the library works correctly. You should see a window with four strange figures :) .
Don't touch StdDraw.java anymore. Now you can easily import StdDraw library and refer to its methods with name of the class.
Enjoy
Related
Good morning everyone!
I did a project x but all my files were out of order so I decided to group them by folders.
foldera
---ClassA.java
---ClassB.java
folderb
---Class1.java
Main.java
The problem arises when I try to compile, since in the main it appears that the classes I made are not found
I thought this could be solved by putting in the classes
package src.foldera.ClassA;
And in the others the same
package src.foldera.ClassB;
And
package src.folderb.Class1;
So in all classes
And in the main put
import src.foldera.*;
import src.folderb.*;
But I keep getting the same error even though I put the packages
It should be noted that I did not create the folders in the code editor, rather I did it in the same Windows 10 File system
What is this about? Thanks!
Assuming a standard setup where the src folder is the root of your source hierarchy, the statements should be:
package foldera;
package folderb;
The imports should be similarly shortened to:
import foldera.*;
import folderb.*;
You have to define the package in which the class is in.
As an example in classA:
package src.foldera;
And in class1:
package src.folderb;
import src.foldera.ClassA;
I'm trying to work off of an existing code base, and one of the files has an import statement accessing the path game.format.noFlash.*. However the format folder only has files for the other classes; the noFlash file folder is nowhere to be found.
I know it must be there because when I begin to type in the import statement in intelliJ, one of the autofill options is the noFlash folder. Is there a way to access it, and if so how?
The auto-fill options are display packages and also class names
I suspect the noFlash is a class and not a folder and Intellij is suggestion that you can import it, for example:
Classes can be specified explicitly on import instead of using the wildcard character.
import javax.swing.JOptionPane; // Make a single class visible.
I am relatively new to java as a disclaimer. I see all kinds of code examples where people "import net...." yet anytime that I try to import anything from this directory, I get an error that the compiler cannot resolve the import net. What have these other programmers done that allows them to use this import? I have seen other people having this problem but I have not seen a straight-forward answer to this question.
For instance:
import net.sourceforge.binge.Xbox360Controller;
When you import an external package, you need to have it in your program during runtime, which means that it either has to exist in YOUR project, or if it is being loaded by another program, then that program has to contain it. To add a library to your eclipse project: see THIS
I imported an external JAR to my project in Eclipse, by following these instructions:
Right click on the project > Build Path > Add external archives > Choosing the JAR file from the hard drive.
The JAR file than appears in the 'References libraries' section in my project, and works fine.
However, I never need to use the import keyword in my classes in order to use the classes from the JAR. I find this weird, I thought I'd have to use import myImportedJar or something similar for this to work.
Is it normal that I don't have to use the import keyword? Did I do something wrong?
The import statement is used to be able to refer to types and their members by their simple names. You don't need to import classes that are in the same package, unless they are nested members of other classes. This is true regardless of where the class comes from, for example, if it's in another .jar.
The import keyword works on a package level. If these packages are supplied by jars or not is not a feature of the java programming language.
import only makes a name available in unqualified form in your program. The following code fragments are identical:
java.util.List<Object> list = new java.util.ArrayList<>()
vs
import java.util.List;
import java.util.ArrayList;
List<Object> list = new ArrayList<>()
Now, importing a jar file in eclipse puts the classes from this jarfile on the classpath - the total "world" of available classes for your application.
I'm currently trying to read some source code in Java I found online to study and learn the material. I want to compile the files first to make sure they work before I study it. When I try to compile though, the compiler complains that it can't find some of the files it needs to import. So opening up the main.java, I find
package br.com.seimos.minijava;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.ArrayList;
import br.com.seimos.minijava.parser.MiniJavaParser;
import br.com.seimos.minijava.syntaxtree.Program;
import br.com.seimos.minijava.visitor.TreeDumper;
import br.com.seimos.minijava.visitor.TreeFormatter;
The errors I'm getting are coming from not being able to find MiniJavaParser, TreeDumper...the 3rd chunk of code. Those files exist in the same directory as the main file though, so what is going on? What is br.com.seimos.minijava stuff? I tried putting the files in that those folders (as in br\com\seimos\minijava\PUT_FILES_HERE) but still no good. Does br need to be in the root directory?
Thanks, I realize this is probably a really elementary question...
The required directory structure is br/com/seimos/minijava/OTHER_FOLDERS/SOURCE_FILES.java. For instance, the path to MiniJavaParser should be br/com/seimos/minijava/parser/MiniJavaParser.java. You should then run the Java compiler from the parent directory of br.
If you're using Eclipse or another IDE, you should configure your project settings to handle this.
For import br.com.seimos.minijava.parser.MiniJavaParser; your MiniJavaParser class must be in the directory br\com\seimos\minijava\parser\ and not br\com\seimos\minijava\. Similarly for other classes. Try changing it.
You're on the right track. You will need to put those files in br/com/seimos/minijava/... as indicated by the package name of each. Java requires that you put files in a directory hierarchy that matches their package names.
Then, you'll want to compile using a command like:
javac br/com/seimos/minijava/parser/MiniJavaParser.java
This is all a bit inconvenient from the command line, especially for a larger project, so you might be better of getting a Java IDE and having it help you arrange the files.