Java

JDK, JRE, JVM

• JDK
• Create java programs. Takes the source code and convert executable format
• Debuggers
• Java compiler (creates the .class files)
• Comes with the JRE in it
• JRE
• Run java program
• Libraries
• Java launcher (the JVM)
• JVM:
• It's a part of the JRE
• It's a machine that only runs java code
• The JVM and be created in many different operating systems
• Java JDK doesn't compile the code for the OS but for the JVM
• It makes java a little slower than the other languages

JAR

• Java Archive: it's similar to a zip, but with extension .jar
• Stores your compiled code (not the source code)

META-INF

• The main method must be specified on jar creation in order to make it executable
• The META-INF folder contains a file called MANIFEST.MF which points to the Main-Class (that contains the main method)