大数据 java 代码示例_Java变量类型与示例

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，

Instance Variables
实例变量
Local Variables
局部变量
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