Eclipse - no Java (JRE) / (JDK) ... no virtual machine
If you see an error message in Eclipse saying "no Java (JRE) / (JDK) ... no virtual machine", it means that Eclipse is unable to find a valid Java installation on your system. This can happen if you have not installed Java or if Eclipse is using an incorrect version of Java.
To fix this error, you need to install a Java Development Kit (JDK) and set it up correctly in Eclipse. Here are the steps:
Download and install a JDK from the Oracle website (http://www.oracle.com/technetwork/java/javase/downloads/index.html). Make sure to download the JDK, not the JRE (Java Runtime Environment).
In Eclipse, go to the "Window" menu and select "Preferences".
In the Preferences window, expand the "Java" node and select "Installed JREs".
Click the "Add" button and select "Standard VM".
In the "JRE Definition" window, click the "Directory" button and browse to the folder where you installed the JDK.
Click "Finish" to add the JDK to Eclipse.
In the "Installed JREs" list, select the JDK you just added and click the "Apply and Close" button.
This should resolve the "no Java (JRE) / (JDK) ... no virtual machine" error and allow you to run Java programs in Eclipse.
Note: If you have multiple Java installations on your system, make sure to select the correct JDK in Eclipse. You may also need to update your system PATH to point to the correct Java executable.