极客笔记Java 菜单驱动程序以检查正数、负数或奇数偶数
如果一个数字大于0，则它被称为正数，如果小于0，则称为负数。负数以减号(-)作为标识。
如果一个数字可以被2整除，则称为偶数，否则称为奇数。在这篇文章中，我们将看到如何使用Java编程语言来检查一个数字是正数、负数还是偶数、奇数。我们将使用switch case实现这个应用程序。
为了向您展示一些示例
实例-1
Suppose the input number is 12.
Checking it as a positive or negative number, it will result 12 as a positive number as it is greater than 0.
实例-2
Suppose the input number is -12.
Checking it as a positive or negative number, it will result -12 as a negative number as it is less than 0.
实例-3
Suppose the input number is 2022.
Checking it as an even or odd number, it will result 2022 as an even number as it is divisible by 2.
实例-4
Suppose the input number is 7.
Checking it as an even or odd number, it will result 7 as an odd number as it is not divisible by 2.
语法
要执行诸如检查一个数字是正数还是负数，或者它是偶数还是奇数这样的操作，我们使用带有一些基本逻辑的“if else语句” 。
以下是 “if else语句” 的语法。
if(condition) {
//code to be executed
}
步骤
步骤-1 - 要求用户输入所需的数字。
步骤-2 - 显示菜单。
步骤-3 - 要求用户输入选择。
步骤-4 - 使用switch case根据选择执行操作。
步骤-5 - 打印结果。
让我们看一个程序来更清楚地理解它。
示例
import java.util.*;
public class Main{
public static void main(String args[]) {
int num;
Scanner inn = new Scanner(System.in);
mainLoop: while (true) {
System.out.println("\n***Menu***");
System.out.println("1. Check if a Number is Positive or Negative");
System.out.println("2. Check Whether a Number is Even or Odd");
System.out.println("3. Terminate the program");
System.out.println("Enter action number (1-3): ");
int command;
if (inn.hasNextInt()){
command = inn.nextInt();
}else {
System.out.println("\nILLEGAL RESPONSE. YOU MUST ENTER A NUMBER.");
inn.nextLine();
continue;
}
switch(command) {
case 1:
System.out.print("Enter a number: ");
num = inn.nextInt();
if(num>0) {
System.out.println("Entered number "+num+" is positive.");
}
//checks the number is less than 0 or not
else if(num<0) {
System.out.println("Entered number "+num+" is negative.");
}
else {
System.out.println("The number is zero.");
}
break;
case 2:
System.out.print("Enter a number: ");
num = inn.nextInt();
if(num % 2 == 0) {
System.out.println("Entered number "+num+" is even.");
}
else {
System.out.println("Entered number "+num+" is odd.");
}
break;
case 3:
System.out.println("Program terminated");
break mainLoop;
default:
System.out.println("Wrong choice!!");
}
}
}
}
输出
***Menu***
1. Check if a Number is Positive or Negative
2. Check Whether a Number is Even or Odd
3. Terminate the program
Enter action number (1-3):
1
Enter a number: 45
Entered number 45 is positive.
***Menu***
1. Check if a Number is Positive or Negative
2. Check Whether a Number is Even or Odd
3. Terminate the program
Enter action number (1-3):
2
Enter a number: 45
Entered number 45 is odd.
***Menu***
1. Check if a Number is Positive or Negative
2. Check Whether a Number is Even or Odd
3. Terminate the program
Enter action number (1-3):
1
Enter a number: -456
Entered number -456 is negative.
***Menu***
1. Check if a Number is Positive or Negative
2. Check Whether a Number is Even or Odd
3. Terminate the program
Enter action number (1-3):
2
Enter a number: 2022
Entered number 2022 is even.
***Menu***
1. Check if a Number is Positive or Negative
2. Check Whether a Number is Even or Odd
3. Terminate the program
Enter action number (1-3):
x
ILLEGAL RESPONSE. YOU MUST ENTER A NUMBER.
***Menu***
1. Check if a Number is Positive or Negative
2. Check Whether a Number is Even or Odd
3. Terminate the program
Enter action number (1-3):
ILLEGAL RESPONSE. YOU MUST ENTER A NUMBER.
***Menu***
1. Check if a Number is Positive or Negative
2. Check Whether a Number is Even or Odd
3. Terminate the program
Enter action number (1-3):
5
Wrong choice!!
***Menu***
1. Check if a Number is Positive or Negative
2. Check Whether a Number is Even or Odd
3. Terminate the program
Enter action number (1-3):
3
Program terminated
在这篇文章中，我们通过使用菜单驱动的方法来探讨了如何在Java中检查一个数字是正数、负数还是偶数、奇数。