"Starting from 0 to learn Java" 1. What are the aspects of object-oriented features

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1. What are the aspects of object-oriented features

1.Java Basic training, starting from 0 to learn Java: abstraction

Abstraction is about ignoring aspects of a topic that are not related to the current goal, so that you can more fully focus on the aspects that are relevant to the current goal. Abstractions do not intend to understand all of the problems, but simply select one part of them, temporarily without some detail. Abstract includes two aspects, one is the process abstraction, the other is the data abstraction.

2.Java Basic training, starting from 0 to learn Java: inheritance

Inheritance is a hierarchical model of a junction class and allows and encourages the reuse of classes, which provides a way to articulate commonalities. A new class of objects can be derived from existing classes, a process known as class inheritance. The new class inherits the attributes of the original class, which is called the derived class (subclass) of the original class, and the original class is called the base class of the new class (The parent Class). Derived classes can inherit methods and instance variables from their base classes, and classes can modify or add new methods to make them more suitable for special needs.

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"Learn java from 0" Java Basic training, what are the aspects of object-oriented features

3.Java Basic training, starting from 0 Java: encapsulation

Encapsulation is the process and data is surrounded, access to data only through the defined interface. Object-oriented computing begins with this basic concept that the real world can be portrayed as a series of fully autonomous, encapsulated objects that access other objects through a protected interface.

4. Java basic training, starting from 0 Java: polymorphism

Polymorphism refers to allowing objects of different classes to respond to the same message. Polymorphism consists of parameterized polymorphism and inclusion polymorphism. Polymorphism language has the advantage of flexibility, abstraction, behavior sharing and code sharing, which solves the problem of application function with the same name.

2. Is string the most basic data type?

The basic data types are byte, int, char, long, float, double, Boolean, and short.

The Java.lang.String class is of the final type, so you cannot inherit the class or modify the class. In order to improve efficiency and save space, we should use the StringBuffer class

3. What is the difference between int and Integer

Java offers two different types: reference types and primitive types (or built-in types). int is the raw data type of Java, and integer is the wrapper class provided by Java for Int. Java provides a wrapper class for each primitive type.

Original type encapsulation class: Booleanboolean charcharacter bytebyte Shortshort

Intinteger Longlong floatfloat doubledouble

The behavior of reference types and primitive types is completely different, and they have different semantics. Reference types and primitive types have different characteristics and usages, including: size and speed issues, which types of data structures are stored as the default values that are specified when reference types and primitive types are used as instance data for a class. The default value of an object reference instance variable is NULL, and the default value of the original type instance variable is related to their type.

Keywords Tags:java training , Java Basic training, starting from 0 To learn Java, Object-oriented

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"Starting from 0 to learn Java" 1. What are the aspects of object-oriented features