Java作业

1.有一对兔子，每三个月生一对兔子，每对小兔子长到三个月之后开始生兔子，问12个月之后一共有多少对兔子（假设没有兔子死），用递归算法实现。

package homework;public class Rabbit {public static void main(String[] args) {for(int i = 1;i<=20;i++){int sum = birth(i);System.out.println(i+"月有"+sum+"对兔子");}}public static int birth(int month){int num;if(month == 1 || month == 2){num = 1;}else if(month == 3){num = birth(month-1)+birth(month-2);}else if(month>=4){num=birth(month-1)+birth(month-3);}else{num=-1;}return num;}}

2.统计大串中小串出现的次数.

package homework;import java.util.Scanner;public class Demo1 {public static void main(String[] args){          System.out.println("请输入一个大串：");          Scanner sc1=new Scanner(System.in);          String bigline=sc1.nextLine();          System.out.println("请输入一个小串：");          Scanner sc2=new Scanner(System.in);          String smallline=sc2.nextLine();                    int count=0;          int x=smallline.length();          for(int i=0;i<bigline.length()-x+1;i++){              String big1=bigline.substring(i,x+i);              if(smallline.compareTo(big1)==0){                  count++;              }             }          System.out.println("在字符串"+bigline+"中，"+smallline+"出现了"+count+"次");          }  }