Download Java and java Official Website

Download Java and java Official Website

Basic Features of object-oriented language:
1. Everything is an object.
2. Programs are a collection of objects. They send messages to each other to tell each other what to do.
3. Each object is its own storage composed of other objects.
4. Each object has its type.
5. All objects of a specific type can receive the same message.

Java access restrictions: public, private, protected.Access restriction not setIs the package access permission.
C ++ is not dynamically bound by default (add virtual). Java is by default, and is more oriented to objects.
Upward Transformation(Multi-state call ),Downward Transformation(Container retrieval Object-parameterized type)
Java Dynamic Memory Allocation Method: all objects are inherited from a single base class Object and can only be created on the stack.
For example: String s = new String ("123"); s in the stack, "123" objects are in the heap, and s points to "123 ".
Concurrent Programming: Java built-in, shared resources: a task locks a resource, completes its tasks, and then releases the resource lock so that other tasks can use this resource.

Object-oriented: Indicates the objects in the problem space, and messages sent to these objects to indicate the behaviors in the space.

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