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Interface and Package.md

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Interface

Interfaces contains;

  • instance methods
  • stataic final varaible
  • no constructor
  • not static method
    • Interfaces allo static method with implementation
      • but it will aginst our use of interface of client view
  • not instance
    • which not client view information

Interfaces are a compile-time construct

  • Used by the Java compiler for type-checking with declared types: to make sure variables are used only where they make sense
  • Recall the rules for declared types and object (dynamic) types
  • Once a Java program compiles, only object types are kept at run-time • Declared types literally “disappear” in the JVM

Package

component family is bundled into its own package, i.e., a grouping of interfaces and classes that the designer thinks “belong together” for logical reasons

Package is provide:

  1. Logical structuring: packages are hierarchical, i.e., you may have packages within packages
  2. A namespace: units in different packages may have the same name without conflict
  3. Another level of access control between public and private