java===String类练习

package cn.china;

public class StringDemo7 {

    public static void main(String[] args) {
        String string = "   dfg   ";
        String s =mytrim(string);
        System.out.println(s);

    }

    public static String mytrim(String string) {
        int start=0;
        int end = string.length()-1;
        while(start<=end && string.charAt(start)==' '){
            start++;
        }
        while(start<=end && string.charAt(end)==' '){
            end--;
        }
        
        return string.substring(start,end+1);
    }

}

package cn.china;

public class StringDemo6 {

    public static void main(String[] args) {
        String s2 = "sdfgsdfghenbas";
        String s1 = "asdfrethenba";
        String s = maxsubstring(s1,s2);
        System.out.println("s="+s);

    }

    public static String maxsubstring(String s1, String s2) {
        String max=null,min=null;
        max=s1.length()>s2.length()?s1:s2;
        min = max.equals(s1)?s2:s1;
        for(int x=0;x<min.length();x++){
            for (int i = 0, y =min.length()-x;y<min.length()+1 ; i++,y++) {/**因为是取子串所以要+1*/
                String s=min.substring(i, y);
                System.out.println(s);
                if(max.contains(s)){
                    return s;
                }
            }
        }
        
        return null;
    }

}

package cn.china;

public class StringDemo5 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String s1 = "nbasdnbasdfnbasdfnbadsnba";
        String s2 = "nba";
        int count = nba_times(s1, s2);
        System.out.println("count="+count);

    }

    public static int nba_times(String s1, String s2) {
        int index = 0;
        int count = 0;
        while ((index = s1.indexOf(s2)) != -1) {
            count++;
            s1 = s1.substring(index + s2.length(), s1.length());
            System.out.println("s1="+s1);
        }
        return count;
    }

}

package cn.china;

public class StringDemo4 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String s1 = "nbasdnbasdfnbasdfnbadsnba";
        String s2 = "nba";
        int count = nba_times(s1,s2);
        System.out.println("count="+count);

    }

    public static int nba_times(String s1, String s2) {
        // TODO Auto-generated method stub
        int count=0;
        int index = 0;
        while((index=s1.indexOf(s2,index))!=-1){
            System.out.println(index);
            count++;
            index=index+s2.length();
        }
        return count;
    }

}

package cn.china;

public class StringDemo3 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        String[]arr = {"ab","cd","ae"};
        printArray(arr);
        sortArray(arr);
        printArray(arr);

    }
    public static void printArray(String [] arr){
        System.out.print("[");
        for(int x=0;x<arr.length;x++){
            if(x!=arr.length-1){
                System.out.print(arr[x]+",");
        }else{
        System.out.println(arr[x]+"]");
        }
            }
    }
    public static void sortArray(String[] arr){
        for(int x = 0;x<arr.length-1;x++){
            for(int y = 0;y<arr.length-1-x;y++){
                if(arr[y].compareTo(arr[y+1])>0){
                    swap(arr,y,y+1);
                }
            }
        }
    } 
    public static void swap(String[]arr,int a,int b){
        String temp=arr[a];
        arr[a]=arr[b];
        arr[b]=temp;
    }
}