Day11_Java_作业

1:递归那个兔子对数练习题
有一对兔子，从出生后第3个月起每个月都生一对兔子，小兔子长到第三个月后每个月又生一对兔子，假如兔子都不死，问第二十个月的兔子对数为多少？(使用递归去解决)
2:定义一个数组,比如:int[] arr = {13,24,57,69,80}使用二分查找查找这个数组中的24元素对应的索引(可以不写这个题,下去预习什么是二分查找)

package Test_book;

/**
 * @author Aoman_Hao
 */
public class Character2 {

    public static void main(String[] args) {
        int[] arr = {13,24,57,69,80};
        String s1 = "24";
        String arr_string = arr.toString();
        for(int i=0;i<arr_string.length();){
            int num2 = (int)(Math.floor(arr_string.length()/2));
            String arr_string_1= arr_string.substring(num2);
            int num = 0;
            num = arr_string_1.indexOf(s1);

            if(num!=-1){
                System.out.println("1索引："+(num+num2));
                break;
            }else if(num==-1){
                String arr_string_2= arr_string.substring(0,num2);
                num = arr_string_2.indexOf(s1);}
                else if(num!=-1){
                System.out.println("2索引："+num);
                break;}
                else{
                    System.out.println("不存在");
                    break;
            }}
        System.out.println("..");
            }
        }

结果运行不出来，之后待调试
3:统计大串中小串出现的次数
举例：在字符串” woaijavawozhenaijavawozhendeaijavawozhendehenaijavaxinbuxinwoaijavagun”中java出
现了5次

package Test_book;

import java.lang.Character.Subset;

import javax.security.auth.Subject;

/**
 * @author Aoman_Hao
 */
public class Character3 {

    public static void main(String[] args) {
        StringBuffer s1 = new StringBuffer("woaijavawozhenaijavawozhendeaijavawozhendehenaijavaxinbuxinwoaijavagun");
        String s11= new String("awa");
        String s2 = s1.toString();
        int sum = 0;


        for(int i=0;i<s2.length();i++){
            int num = s2.indexOf(s11);
            if(num !=-1){
                sum++;
                s2 = s2.substring(num+s11.length());
            }else if(num ==-1){
                System.out.println("字符串"+s1+"不包含字符串"+s11);
                break;
            }
        }
        if(sum != 0){
            System.out.println("字符串'"+s1+"'包含'"+s11+"'字符串 "+sum+"个");
        }
    }

}