二、Java方法对应练习

1.实现一个函数，检测一个年份是否为闰年

import java.util.Scanner;  
public class ImplementAFunctionThatDetectsIfAYearIsALeapYear {  public static void main(String[] args) {  System.out.println("请输入一个年份");  Scanner scanner = new Scanner(System.in);  int year = scanner.nextInt();  System.out.println(isLeapYear(year));  }  public static boolean isLeapYear(int year) {  return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);  }  
}

2.实现一个两个整数相加的方法

import java.util.Scanner;  
public class ImplementAMethodOfAddingTwoIntegers {  public static void main(String[] args) {  Scanner scanner = new Scanner(System.in);  System.out.println("请输入两个数字");  int a = scanner.nextInt();  int b = scanner.nextInt();  System.out.println(isAdd(a, b));  }  public static int isAdd(int a, int b)  {  return a + b;  }  
}

3.递归求阶乘

import java.util.Scanner;  public class RecursiveSearchForOrders {  public static void main(String[] args) {  Scanner scanner = new Scanner(System.in);  System.out.println("请输入一个数字");  int number = scanner.nextInt();  System.out.println(search(number));  }  public static int search(int n) {  if (n == 1) {  return 1;  } else {  return n * search(n - 1);  }  }  
}

4.递归按顺序打印一个数字的每一位（例如1234打印出1 2 3 4）

import java.util.Scanner;  public class RecursiveOrderPrinting {  public static void main(String[] args) {  Scanner scanner = new Scanner(System.in);  System.out.println("请输入一个数字");  print(scanner.nextInt());  scanner.close();  }  public static void print(int n) {  if(n / 10 < 1)  {  System.out.print(n % 10 + " ");  return;  }  print(n / 10);  System.out.print(n % 10 + " ");  }  
}

5. 递归求1+2+3+…+10

public class RecursiveSum {  public static void main(String[] args) {  System.out.println(recursiveSum(10));  }  public static int recursiveSum(int n) {  if (n == 1) {  return 1;  }  return n + recursiveSum(n - 1);  }  
}

6.写一个递归方法，输入一个非负整数，返回组成它的数字之和，例如，输入1729，则应该返回1+7+2+9，它的和是19

public class RecursionPleaseSumEveryone {  public static void main(String[] args) {  System.out.println(everyoneSum(1729));  }  public static int everyoneSum(int n) {  if (n / 10 < 1) {  return n % 10;  }  return (n%10) + everyoneSum(n/10);  }  
}

7.求斐波那契数列的第N项

import java.util.Scanner;  public class FindTheNthFibonacci {  public static void main(String[] args) {  Scanner scanner = new Scanner(System.in);  System.out.println("请输入一个数字");  System.out.println(fib(scanner.nextInt()));  }  public static int fib(int n) {  if (n <= 1) {  return n;  }  return fib(n - 1) + fib(n - 2);  }  
}