How to Check if Java Is Installed

1. Use java -version Command in Windows to Check if Java Is Installed
2. Use where java to Search for Java in Windows
3. Use which java to Check for Java Installation in Mac
4. Use System.getProperty("java.version") to Check Java Version in Java

This tutorial teaches us to check if Java is installed on the machine. Some software and applications require Java, and to check if our device supports it, we need to follow the below steps.

Use java -version Command in Windows to Check if Java Is Installed

The quickest way to check if there is any installation of Java available in Windows is to use the java command with the -version option in a command line.

We get details like the Java Development Kit (JDK) version, the runtime environment, and the server machine in the output when we run the command.

C:\WINDOWS\system32>java -version

Output:

openjdk version "15.0.1" 2020-10-20
OpenJDK Runtime Environment (build 15.0.1+9-18)
OpenJDK 64-Bit Server VM (build 15.0.1+9-18, mixed mode, sharing)

Use where java to Search for Java in Windows

Another way to find out if Java is installed on our Windows device is to use the where command that searches out the specified name of the executable and returns its location.

To check for Java, we use where java in the command line, and if Java is installed on our device, it will return the location of java.exe.

C:\WINDOWS\system32> where java

C:\Users\User1\.jdks\openjdk-15.0.1\bin\java.exe

Use which java to Check for Java Installation in Mac

The equivalent of the where command in Mac is which that does the same operation as where and returns the file’s location. We use the command which java in the terminal of the Mac device, and if Java is installed, it returns the location of the Java.

> which java

/Users/User1/.jenv/shims/java

Use System.getProperty("java.version") to Check Java Version in Java

We can check if Java is installed programmatically using the getProperty() function of the System class that returns system properties.

We create a Java program, and in the print statement, we call the getProperty() from the System class and pass the java.version as an argument.

In the output, we get the version of the installed Java that proves that a version of Java is installed on the machine.

public class ExampleClass1 {
  public static void main(String[] args) {
    System.out.println(System.getProperty("java.version"));
  }
}

Output:

15.0.1

Note that the above steps might not work if we have not set Java’s path as a global variable.