# Java 程序：计算正方形的面积

> 原文： [https://beginnersbook.com/2014/01/java-program-to-calculate-area-of-square/](https://beginnersbook.com/2014/01/java-program-to-calculate-area-of-square/)

在本教程中，我们将学习**如何计算正方形**的面积。以下是两种方法：

1）程序 1：提示用户输入正方形的边长

2）程序 2：在程序的源代码中指定正方形的边长。

**计划 1：**

```java
/**
 * @author: BeginnersBook.com
 * @description: Program to Calculate Area of square.Program 
 * will prompt user for entering the side of the square.
 */
import java.util.Scanner;
class SquareAreaDemo {
   public static void main (String[] args)
   {
       System.out.println("Enter Side of Square:");
       //Capture the user's input
       Scanner scanner = new Scanner(System.in);
       //Storing the captured value in a variable
       double side = scanner.nextDouble();
       //Area of Square = side*side
       double area = side*side; 
       System.out.println("Area of Square is: "+area);
   }
}
```

输出：

```java
Enter Side of Square:
2.5
Area of Square is: 6.25
```

**计划 2：**

```java
/**
 * @author: BeginnersBook.com
 * @description: Program to Calculate Area of square.
 * No user interaction: Side of square is hard-coded in the
 * program itself.
 */
class SquareAreaDemo2 {
   public static void main (String[] args)
   {
       //Value specified in the program itself
       double side = 4.5;
       //Area of Square = side*side
       double area = side*side; 
       System.out.println("Area of Square is: "+area);
   }
}
```

输出：

```java
Area of Square is: 20.25
```