大數據 java 代碼示例

Java變量 (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.

變量是用戶定義的存儲塊名稱，它們的值可以在程序執行期間隨時更改。 它們在類/程序中起著重要的作用，因為它們有助于存儲，檢索數據值。

Java中變量的類型 (Types of the variables in Java)

There are three types of Java variables,

Java變量有三種類型 ，

1. Instance Variables

   實例變量

2. Local Variables

   局部變量

3. Class/Static Variables

   類/靜態變量

1)實例變量 (1) Instance Variables)

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

  實例變量在類中聲明，但在方法，塊或構造函數之外。

• Instance variables have a default value 0.

  實例變量的默認值為0 。

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

  僅當創建類的對象時才能創建這些變量。

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

輸出量

Color of the bike is Red

2)局部變量 (2) Local Variables)

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

  局部變量是在類方法中聲明的變量。

• We can use these variables within a block only.

  我們只能在一個塊中使用這些變量。

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

輸出量

Teacher age is : 10

3)類變量/靜態變量 (3) Class Variables/Static Variables)

• This can be called Both Class and Static Variable.

  這可以稱為類和靜態變量 。

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

  這些變量只有一個副本，該副本由類中的所有不同對象共享。

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

  它在程序執行開始時創建，并在程序結束時銷毀。

• Its Default value is 0.

  其默認值為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

輸出量

Number of tyres are 6

翻譯自: https://www.includehelp.com/java/variables-types-with-examples.aspx

大數據 java 代碼示例