java学习之string编程题

1  统计某个字符在目标字符串中出现的次数

public class test{

    public static void main(String[] args){

    String str="李荣lir999ong4567899";

    String c="9";

    int j=0;

//    char[] arr=str.toCharArray();

        for(int i=0;i

        String b =str.charAt(i)+"";

        

            if(b.equals(c)){

            

                j=j+1;

            }

        }

    System.out.println(j);    

    }

}

2  实现字符串逆序    字符串的旋转

public class test{

    public static void main(String[] args){

    

    String ss="abcdefg";

    StringBuffer sb=new StringBuffer();

        for(int i=ss.length()-1;i>=0;i--){    

        sb.append(ss.charAt(i));        

        }    

    System.out.println(sb.toString());    

    }

}

3   去掉字符串中的特殊字符

public class test{

    public static void main(String[] args){

    String str="123.456.78.56";

    String[] arr= str.split("\\.");

    

    StringBuffer sb=new StringBuffer();

        for(int i=0;i

        

            sb.append(arr[i]);

        }

        System.out.println(sb.toString());

    

    }}

    

4  去除字符串中的重复字符

public class test{

    public static void main(String[] args){

    String str="123.456.78.56";

    String[] arr= str.split("\\.);

    

    StringBuffer sb=new StringBuffer();

        for(int i=0;i

        

            sb.append(arr[i]);

        }

        System.out.println(sb.toString());

    

    }}

5  统计字符串中每个字符出现的次数

public class test{

    public static void main(String[] args){

    String str="ssd1dfffgggg";

        int len=str.length();

        HashMap map=new HashMap();

            for(int i=0;i

            

            String cc=str.charAt(i)+"";

            Integer inte=map.get(cc);

                if (inte==null){

                map.put(cc,1);

                }

                else{

                map.put(cc,inte.intValue()+1);

                }                

            }                

        System.out.println(map);        

    }}