一、应用要求

　　输入一个字符串，再输入要查找的字符，判断该字符在该字符串中出现的次数。

二、实现思路

　　1.使用substring()方法将字符串的每个字符存入数组

　　2.比较数组每个字符是否与指定的字符相等，并计数

三、编写代码

　　错误案例：

1 import java.util.Scanner; 2  3 public class StringDemo { 4  5     public static void main(String[] args) { 6         Scanner input = new Scanner(System.in); 7         System.out.println("请输入一句话："); 8         String string = input.next(); 9         System.out.println("请输入查找的字符串：");10         String s = input.next();11         12         13         //2.正序14         /*int num = 0;15         int temp = 0;16         while(string.indexOf(s)>-1){17             int index = string.indexOf(s);18             num=num+index+temp;19             System.out.print(num+"\t");20             string = string.substring(index+1);21             temp++;22         }*/23         /*while(string.indexOf(s)>-1){24             if (temp == 0) {25                 System.out.println(string.indexOf(s));26                 num = string.indexOf(s);27                 string = string.substring(string.indexOf(s)+1);28                 temp++;29             } else {30                 int indexs = string.indexOf(s);31                 string = string.substring(indexs+1);32                 num=num+indexs+1;33                 System.out.print(num+"\t");34             }35             36         }*/37         /*从后往前找，遇到重复字符会出错38          * 39         //1.查找第一个下标40         int index = string.indexOf(s);41         //声明一个集合保存获取的下标42         List
     
       list = new ArrayList
      
       ();43         while(string.length()>=index){44             //2.查找最后一个45             int indexEnd = string.lastIndexOf(s);46             if (indexEnd<0) {47                 break;48             }49             list.add(indexEnd);//保存到list50             //System.out.print(indexEnd+"\t");51             string = string.substring(0, indexEnd);52         }53         //遍历list54         System.out.println();55         for (int i = list.size()-1; i >= 0; i--) {56             System.out.print(list.get(i)+"\t");57         }58         */59         //查找字符打印位置下标：正序查找才是王道60         for (int i = 0; i <= string.lastIndexOf(s); i++) {61             if (s.equals(string.substring(i, i+s.length()))) {62                 System.out.println(i);63                 i = i+s.length()-1;64             }65         }66         input.close();67 68     }69 70 }
      
     

　　最终代码：

1 import java.util.Scanner; 2 /** 3  * 查找字符串 4  * @author Administrator 5  * 6  */ 7 public class String01 { 8  9     public static void main(String[] args) {10         Scanner input = new Scanner(System.in);11         System.out.println("请输入一句话：");12         String string = input.next();13         System.out.print("请输入查找的字符串：");14         String s = input.next();15         //查找字符打印位置下标16         int count = 0;//记录字符出现的次数17         for (int i = 0; i <= string.lastIndexOf(s); i++) {18             if (s.equals(string.substring(i, i+s.length()))) {19                 System.out.print(i+"\t");20                 i = i+s.length()-1;21                 count++;22             }23         }24         System.out.println(s+"共出现"+count+"次！");25         input.close();26 27     }28 29 }