Java练习题

1、取出一个字符串中字母出现的次数。如：字符串："abcdekka27qoq" ，输出格式为：a(2)b(1)k(2)...

import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.TreeMap;

public class Test1 {
    public static void main(String[] args){
        String str ="abcdekka27qoq";
        System.out.println(charCount(str));
    }
    public static String charCount(String str){
        char[] chs = str.toCharArray();
        Map<Character,Integer> m = new TreeMap<Character,Integer>();
        int count =0;
        for(int x=0;x<chs.length;x++){
            if(chs[x]>='a'&&chs[x]<='z'||chs[x]>='A'&&chs[x]<='Z'){
                Integer value = m.get(chs[x]);
                if(value!=null)
                    count=value;
                count++;
                m.put(chs[x], count);
                count =0;
            }
        }
        StringBuilder sb =new StringBuilder();
        Set<Map.Entry<Character,Integer>> s = m.entrySet(); 
        Iterator<Entry<Character, Integer>> it =s.iterator();
        while(it.hasNext()){
            Map.Entry<Character, Integer> me =it.next();
            sb.append(me.getKey()+"("+me.getValue()+")");
        }
        return sb.toString();
        
    }
}

 2.根据上排给出的十个数，在其下排填出对应的十个数，要求下排每个数都是上排十个数在下排出现的次数

/*
 
根据上排给出的十个数，在其下排填出对应的十个数，要求下排每个数都是上排十个数在下排出现的次数
 
*/
 
class GetNextArray
 
{
 
        public static void main(String[] args) 
        {
 
                //System.out.println("Hello World!");
 
                int[] arr1={0,1,6,3,5,4,2,7,8,9};
 
                int[] arr2=new int[arr1.length];
 
                for(int y=0;y<arr1.length;y++)
 
                {
 
                        for (int x=0;x<arr1.length ;x++ )
 
                        {
 
                                int a=getCount(arr1[x],arr2);
 
                                                
                                if(arr2[0]==0)
 
                                        arr2[0]=a-1;
 
                                else
 
                                        arr2[x]=a;                                                
                        }
 
                }
 
                printArray(arr1);
 
                System.out.println();
 
                printArray(arr2);
 
        }
 
        //获得每个元素在数组中出现的次数
 
        public static int getCount(int key,int[] arr)
 
        {
 
                int count=0;
 
                for (int x=0;x<arr.length ;x++ )
 
                {
 
                        if (key==arr[x])
 
                                count++;                        
                }
 
                return count;
 
        }
 
        //打印数组        
        public static void printArray(int[] arr)
 
        {
 
                for (int x=0;x<arr.length ;x++ )
 
                {
 
                        if(x!=arr.length-1)
 
                                System.out.print(arr[x]+",");
 
                        else
 
                                System.out.print(arr[x]);
 
                }
 
        }
 
}