Open Command Prompt or Terminal
Type `java -version`
Press Enter
If Java is installed, the version information will appear
If Java is not installed, an error message will appear
Type `javac -version`
Press Enter
If the Java compiler is installed, its version information will appear
If the command is not recognized, Java may not be installed or may not be added to PATH
On Windows, type `where java`
On macOS or Linux, type `which java`
Check the installed programs list on your system
Check the Java installation folder on your system
Verify the `JAVA_HOME` environment variable if needed