what is the use of jar file in java
JAR (file format) A JAR (Java ARchive) is a package file format typically used to aggregate many Java class files and associated metadata and resources (text, images, etc.) into one file for distribution.[3]
Java package In Java 9, "modules", a kind of collection of packages, are planned as part of Project Jigsaw; these were earlier called "superpackages" and originally planned for Java 7.
Java virtual machine The aim is binary compatibility. Each particular host operating system needs its own implementation of the JVM and runtime. These JVMs interpret the bytecode semantically the same way, but the actual implementation may be different. More complex than just emulating bytecode is compatibly and efficiently implementing the Java core API that must be mapped to each host operating system.
Command-line interface Today, many end users rarely, if ever, use command-line interfaces and instead rely upon graphical user interfaces and menu-driven interactions. However, many software developers, system administrators and advanced users still rely heavily on command-line interfaces to perform tasks more efficiently, configure their machine, or access programs and program features that are not available through a graphical interface.
Return type You declare a method's return type in its method declaration. Within the body of the method, you use the return statement to return the value.
Denial-of-service attack A wide array of programs are used to launch DoS-attacks.