To check if the Java JDK (Java Development Kit) is installed on your Mac, follow these steps:
If Java is installed on your Mac, you should see a message displaying the version of Java that is installed. If Java is not installed, you will see an error message indicating that the "javac" command is not recognized.
Alternatively, you can also check if Java is installed by going to System Preferences > Java. If Java is installed, you should see a Java icon in the System Preferences window. You can also check the version of Java by clicking the "About" button in this window.