Detailed explanation of Java environment variable configuration steps under Linux system

Detailed explanation of Java environment variable configuration steps under Linux system

1. Overview:
In Linux system, if we need to use Java to develop or run Java programs , you need to configure Java environment variables. Java environment variables include JAVA_HOME, PATH and CLASSPATH. This article will detail the steps to configure Java environment variables under Linux systems and provide specific code examples.

2. Configuration steps:

1. Download and install Java Development Kit (JDK).
   First, we need to download the JDK installation package suitable for Linux systems from the Oracle official website (http://www.oracle.com/technetwork/java/javase/downloads/index.html) and follow the instructions of the installation package to complete it. JDK installation.
2. Determine the JDK installation path.
   In Linux systems, JDK is installed in the directory /opt/jdk by default, but the actual installation path may be different, so we need to determine the actual installation path of JDK.

3. Configure the JAVA_HOME variable.
   Open the Terminal window and enter the following command in the command line:

   sudo gedit ~/.bashrc

   In the open text editor, add the following content at the end of the file:

   export JAVA_HOME=/usr/lib/jvm/java-8-oracle

   Among them, / usr/lib/jvm/java-8-oracle should be replaced with the actual path to the JDK, save and close the file.

4. Configure the PATH variable.
   In the terminal, enter the following command:

   sudo gedit /etc/environment

   In the opened file, find the definition of the PATH variable and add the JDK bin directory path after it. For example:

   PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/usr/lib/jvm/java-8-oracle/bin"

   Save and close the file.

5. Configure CLASSPATH variable (optional).
   If you need to use Java class library, we can configure the CLASSPATH variable. In the terminal, enter the following command:

   sudo gedit ~/.bashrc

   Add the following at the end of the open file:

   export CLASSPATH=.:$JAVA_HOME/lib

   Save and close the file.

6. Variables that take effect.
   In the terminal, execute the following command to make the configured environment variables take effect:

   source ~/.bashrc

   Or, directly close the terminal window and reopen a new terminal window.

7. Verify the configuration results.
   In the terminal, enter the following command to verify whether the JAVA_HOME and PATH variables are configured correctly:

   echo $JAVA_HOME
   echo $PATH

   If the output results are the installation path of the JDK and the path to the bin directory containing the JDK, the configuration is successful. .

3. Code example:
The following is a simple Java program example (HelloWorld.java):

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

In the terminal, compile and Run the program:

javac HelloWorld.java
java HelloWorld

If "Hello, World!" is successfully output, it means that the Java environment variable is configured successfully.

Summary:
Configuring Java environment variables is a prerequisite for using Java to develop or run Java programs in a Linux system. This article details the steps to configure Java environment variables under Linux systems and provides specific code examples. I hope this article can be helpful to readers who need to develop Java in Linux systems.

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