大数据 java 代码示例

Java变量 (Java variables)

Variables are the user-defined names of the memory blocks, and their values can be changed at any time during program execution. They play an important role in a class/program as they help in to store, retrieve a data value.

变量是用户定义的存储块名称，它们的值可以在程序执行期间随时更改。 它们在类/程序中起着重要的作用，因为它们有助于存储，检索数据值。

Java中变量的类型 (Types of the variables in Java)

There are three types of Java variables,

Java变量有三种类型 ，

1. Instance Variables

   实例变量

2. Local Variables

   局部变量

3. Class/Static Variables

   类/静态变量

1)实例变量 (1) Instance Variables)

• Instance variables are declared in a class but outside a Method, Block or Constructor.

  实例变量在类中声明，但在方法，块或构造函数之外。

• Instance variables have a default value 0.

  实例变量的默认值为0 。

• These variables can be created only when the object of a class is created.

  仅当创建类的对象时才能创建这些变量。

Example:

例：

public class Bike {
       public String color;    Bike(String c) {
           color = c;    }    public void display() {
           System.out.println("color of the bike is " + color);    }    public static void main(String args[]) {
           Bike obj = new Bike("Red");        obj.display();    }}

Output

输出量

Color of the bike is Red

2)局部变量 (2) Local Variables)

• Local variables are the variables which are declared in a class method.

  局部变量是在类方法中声明的变量。

• We can use these variables within a block only.

  我们只能在一个块中使用这些变量。

Example:

例：

public class TeacherDetails {
       public void TeacherAge() {
           int age = 0;        age = age + 10;        System.out.println("Teacher age is : " + age);    }    public static void main(String args[]) {
           TeacherDetails obj = new TeacherDetails();        obj.TeacherAge();    }}

Output

输出量

Teacher age is : 10

3)类变量/静态变量 (3) Class Variables/Static Variables)

• This can be called Both Class and Static Variable.

  这可以称为类和静态变量 。

• These variables have only one copy that is shared by all the different objects in a class.

  这些变量只有一个副本，该副本由类中的所有不同对象共享。

• It is created during the start of program execution and destroyed when the program ends.

  它在程序执行开始时创建，并在程序结束时销毁。

• Its Default value is 0.

  其默认值为0 。

Example:

例：

public class Bike {
       public static int tyres;    public static void main(String args[]) {
           tyres = 6;        System.out.println("Number of tyres are " + tyres);    }}

Output

输出量

Number of tyres are 6

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大数据 java 代码示例