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在菜单驱动的程序或游戏中，我们需要一个选项来重新启动或重置我们的程序。 我们可以通过递归调用函数或使用条件循环语句来重新启动Java中的程序。

使用 do-while 条件语句

import java.util.*;
import java.util.Scanner;


class Main
{

  public static int addNumbers(int a, int b)
  {
    return a + b;
  }

  public static void main(String[] args)
  {
    boolean flag=false;

    Scanner sc= new Scanner(System.in);
    do
    {
    System.out.print("Enter the first number: ");
    int num1= sc.nextInt();
    System.out.print("Enter the second number: ");
    int num2= sc.nextInt();
    int result = addNumbers(num1, num2);
    System.out.println("The sum is: " + result);
    System.out.print("Do you want to add more numbers? Enter y for yes and n for no. ");
    char input = sc.next().charAt(0);
    if(input == 'y')
    {
        flag=true;
    }
    else
    {
        flag=false;
    }
    }while(flag);

  }
}

输出:

Enter the first number: 8
Enter the second number: 7
The sum is: 15
Do you want to add more numbers? Enter y for yes and n for no. y
Enter the first number: 9
Enter the second number: 4
The sum is: 13
Do you want to add more numbers? Enter y for yes and n for no. n

上面的代码显示了用于再次重新启动函数的条件循环的功能； 只要用户输入y，程序就会重新启动。

使用不带停止条件的 do-while 条件语句

import java.util.*;
import java.util.Scanner;


class Main
{

  public static int addNumbers(int a, int b)
  {
    return a + b;
  }

  public static void main(String[] args)
  {
    boolean flag=true;

    Scanner sc= new Scanner(System.in);
    do
    {
    System.out.print("Enter the first number: ");
    int num1= sc.nextInt();
    System.out.print("Enter the second number: ");
    int num2= sc.nextInt();
    int result = addNumbers(num1, num2);
    System.out.println("The sum is: " + result);
    }while(flag);

  }
}

输出:

Enter the first number: 8
Enter the second number: 7
The sum is: 15
Enter the first number: 9
Enter the second number: 4
The sum is: 13
Enter the first number: .....

上面的代码显示了条件循环的功能，用于无限次重新启动函数。 阻止程序重新启动的唯一方法是关闭程序。

使用递归重新启动程序

import java.util.*;
import java.util.Scanner;


class Main
{

  public static void addNumbers(int a, int b, int c)
  {
    Scanner sc= new Scanner(System.in);
    if (c==0)
    {
        int result= a + b;
        System.out.println("The sum is: " + result);
        return;
    }
    int result= a + b;
    System.out.println("The sum is: " + result);
    System.out.print("Enter the first number: ");
    int num1= sc.nextInt();
    System.out.print("Enter the second number: ");
    int num2= sc.nextInt();
    c--;
    addNumbers(num1,num2,c);
  }

  public static void main(String[] args)
  {
    Scanner sc= new Scanner(System.in);
    System.out.print("Enter the first number: ");
    int num1= sc.nextInt();
    System.out.print("Enter the second number: ");
    int num2= sc.nextInt();
    System.out.print("How many times do you want to restart this program? : ");
    int num3= sc.nextInt();
    addNumbers(num1, num2, num3);

  }
}

输出:

Enter the first number: 5
Enter the second number: 6
How many times do you want to restart this program? : 2
The sum is: 11
Enter the first number: 4
Enter the second number: 5
The sum is: 9
Enter the first number: 7
Enter the second number: 8
The sum is: 15

上面的代码显示了递归函数的功能，用于再次重新启动自身。 该程序将根据用户需要重新启动多次。

使用递归在没有停止条件的情况下重新启动程序

import java.util.*;
import java.util.Scanner;


class Main
{

  public static void addNumbers()
  {
    Scanner sc= new Scanner(System.in);
    System.out.print("Enter the first number: ");
    int num1= sc.nextInt();
    System.out.print("Enter the second number: ");
    int num2= sc.nextInt();
    int result= num1+num2;
    System.out.println("The sum is: " + result);
    addNumbers();
  }

  public static void main(String[] args)
  {
    addNumbers();

  }
}

输出:

Enter the first number: 5
Enter the second number: 3
The sum is: 8
Enter the first number: 8
Enter the second number: 11
The sum is: 19
Enter the first number: ...

上面的代码显示了递归函数的功能，用于再次重新启动自身。 由于递归调用周期中没有停止条件，因此程序将无限次重新启动。