/FirstOne_Java

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Java Examples

See repository with source code for Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

This is how to compile a class in a package passing the current directory as the class path (for the sake of example as this is the default behavior) so other classes can be found.

Note how the class is run with the java command using its qualified name (com.zinibu.common.FirstSample) and from the directory (src) containing the root of the package (com).

$ pwd
/home/alexis/Projects/FirstOne_Java/src
javac -cp . com/zinibu/common/FirstSample.java
java com.zinibu.common.FirstSample

Another example.

$ pwd
/home/alexis/Projects/FirstOne_Java/src
$ javac -cp ~/Projects/FirstOne_Java/src/ com/zinibu/algs4/QuickTest.java
$ java com.zinibu.algs4.QuickTest

And using the implicit current directory as the class path

$ javac com/zinibu/algs4/QuickTest.java
$ java com.zinibu.algs4.QuickTest

A finally, compiling and running the original source code of the Algorithms book from the directory (src) containing the root of the package (edu). In this case there's no need to modify the class path because the current directory is used to the search by default.

$ javac edu/princeton/cs/algs4/BinarySearch.java
$ java edu.princeton.cs.algs4.BinarySearch ~/Downloads/algs4-data/tinyW.txt < ~/Downloads/algs4-data/tinyT.txt

For a .jar or .zip file that contains .class files, the class path ends with the name of the .zip or .jar file. For .class files in an unnamed package, the class path ends with the directory that contains the .class files. For .class files in a named package, the class path ends with the directory that contains the "root" package (the first package in the full package name). Multiple path entries are separated by semi-colons. With the set command, it's important to omit spaces from around the equals sign (=).

The default class path is the current directory. Setting the CLASSPATH variable or using the -classpath command-line option overrides that default, so if you want to include the current directory in the search path, you must include "." in the new settings.

When using multiple class paths, remember that the Windows path separator is ; and the Linux path separator is :.

Windows:

$ java -cp file.jar;dir/* my.app.ClassName

Linux:

$ java -cp file.jar:dir/* my.app.ClassName

Read more about the class path <http://docs.oracle.com/javase/7/docs/technotes/tools/windows/classpath.html>_.

Tests with binary search

Change to the directory that contains the "root" package. This is the first package in the full package name; src/com/zinibu/algs4/BinarySearch.java uses two packages, com and edu, so this directory is src.

$ pwd
/home/alexis/Projects/FirstOne_Java/src

Compile using the default class path, the current directory (.), and that will create the required classes,

$ javac com/zinibu/algs4/BinarySearch.java
edu/princeton/cs/algs4/In.class
edu/princeton/cs/algs4/StdIn.class
edu/princeton/cs/algs4/StdOut.class
com/zinibu/algs4/BinarySearch.class

and now you can run the BinarySearch class with

$ java com.zinibu.algs4.BinarySearch  ~/Downloads/algs4-data/tinyW.txt < ~/Downloads/algs4-data/tinyT.txt

You can also compile using algs4.jar, which contains all the classes for the book (we're still in the src directory).

$ javac -cp ../lib/algs4.jar com/zinibu/algs4/BinarySearch.java
$ java -cp ../lib/algs4.jar:. com.zinibu.algs4.BinarySearch  ~/Downloads/algs4-data/tinyW.txt < ~/Downloads/algs4-data/tinyT.txt

In this case you need add the current directory (the dot at the end of -cp ../lib/algs4.jar:.) to the class path.

[~/IdeaProjects/FirstProject/out/production/FirstProject]
$ java -cp /home/alexis/IdeaProjects/FirstProject/out/production/FirstProject com.zinibu.basic.Example
Hi
toyota 1997
[~/IdeaProjects/FirstProject/out/production/FirstProject]
$ java -cp . com.zinibu.basic.Example
Hi
toyota 1997

Running algs4 classes from the command line:

First,

cd /path-to/FirstOne
  1. Recommended, passing classpath via -cp:
java -cp /home/alexis/IdeaProjects/FirstOne/lib/algs4.jar edu.princeton.cs.algs4.BinarySearch ~/Downloads/algs4-data/tinyW.txt < ~/Downloads/algs4-data/tinyT.txt

But, this is important, to provide more than one classpath, because I want to modify the source for BinarySearch and recompile it to /home/alexis/IdeaProjects/FirstOne/out/production/FirstOne while using libraries from /home/alexis/IdeaProjects/FirstOne/lib/algs4.jar, compile from IDEA and run from the command line:

java -cp "/home/alexis/IdeaProjects/FirstOne/out/production/FirstOne:/home/alexis/IdeaProjects/FirstOne/lib/algs4.jar" edu.princeton.cs.algs4.BinarySearch ~/Downloads/algs4-data/tinyW.txt < ~/Downloads/algs4-data/tinyT.txt

I have the class with the main method in both algs4.jar and /home/alexis/IdeaProjects/FirstOne/src so it's important to indicate the class paths order.

Another example running from the parent directory where the classes are, in this example: /home/alexis/IdeaProjects/FirstOne/out/production

$ pwd
/home/alexis/Learn/FirstOne_Java/out/production/FirstOne_Java
[~/Learn/FirstOne_Java/out/production/FirstOne_Java] master
$ java -cp "/home/alexis/Learn/FirstOne_Java/out/production/FirstOne_Java:/home/alexis/Learn/FirstOne_Java/lib/algs4.jar" com.zinibu.algs4.BinarySearch /home/alexis/Learn/algs4/data/tinyW.txt < /home/alexis/Learn/algs4/data/tinyT.txt

Let's do some binary search

And some initial tests

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  1. Using CLASSPATH environment variable
export CLASSPATH=/home/alexis/IdeaProjects/FirstOne/lib/algs4.jar
echo $CLASSPATH
java edu.princeton.cs.algs4.BinarySearch ~/Downloads/algs4-data/tinyW.txt < ~/Downloads/algs4-data/tinyT.txt

Packages

For convenience, the Java compiler automatically imports two entire packages for each source file: (1) the java.lang package and (2) the current package (the package for the current file). Read more about packages.