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本文将演示如何在不使用数组的情况下在 Java 中反转整数。

在不使用数组的情况下反转整数时，我们需要遵循三个步骤。

• 使用模 (%) 运算符查找整数的余数。
• 将变量 reverse 乘以 10，然后将其与余数相加。
• 将数字除以 10。

在 Java 中使用递归来反转整数

递归是使用模数和除法运算符反转整数的最简单方法。

例子：

import java.util.Scanner;
public class Reverse_Recursion {
  // Create a method to reverse a number using recursion
  public static void Recursion_reverse(int input_number) {
    if (input_number < 10) {
      // If the number is less then 10 then no need to reverse
      System.out.println(input_number);
      return;
    } else {
      System.out.print(input_number % 10);
      Recursion_reverse(input_number / 10);
    }
  }
  public static void main(String args[]) {
    System.out.print("Enter the Integer you want to Reverse: ");
    Scanner input_num = new Scanner(System.in);
    int input_number = input_num.nextInt();
    System.out.print("The reverse of the given number using recursion is: ");
    Recursion_reverse(input_number);
  }
}

输出：

Enter the Integer you want to Reverse: 1234567890
The reverse of the given number using recursion is: 0987654321

在 Java 中使用 while 循环反转整数

要使用 while 循环反转整数，我们必须遵循提到的所有三个步骤。

例子：

import java.util.Scanner;
public class Reverse_While {
  public static void main(String args[]) {
    System.out.print("Enter the Integer you want to Reverse: ");
    Scanner input_num = new Scanner(System.in);
    int input_number = input_num.nextInt();
    int reverse_number = 0;
    while (input_number != 0) {
      int remainder_number = input_number % 10;
      reverse_number = reverse_number * 10 + remainder_number;
      input_number = input_number / 10;
    }
    System.out.println("The reverse of the given number using while loop is: " + reverse_number);
  }
}

输出：

Enter the Integer you want to Reverse: 123456789
The reverse of the given number using while loop is: 987654321

在 Java 中使用 for 循环反转整数

for 循环也类似于 while 循环反转整数。

这次让我们尝试反转一个负整数。

例子：

import java.util.Scanner;
public class Reverse_For {
  public static void main(String args[]) {
    System.out.print("Enter the Integer you want to Reverse: ");
    Scanner input_num = new Scanner(System.in);
    int input_number = input_num.nextInt();
    int reverse_number = 0;
    for (; input_number != 0; input_number = input_number / 10) {
      int remainder_number = input_number % 10;
      reverse_number = reverse_number * 10 + remainder_number;
    }
    System.out.println("The reverse of the given number using while loop is: " + reverse_number);
  }
}

Enter the Integer you want to Reverse: -123456789
The reverse of the given number using while loop is: -987654321