關於String的簡單編程題__string

一、將字串反轉

package string;public class Reverse {    public static void main(String[] args) {        String s1 = "abc   defg wf";        //用字串轉字元數組實現反轉        String s2 = "";        char[] cs = s1.toCharArray();        for (int i = cs.length - 1; i >= 0; i--) {            s2 = s2 + cs[i];        }        System.out.println("方法一反轉操作後為:" + s2);        //利用StringBuffer的reverse()方法實現反轉        StringBuffer sb = new StringBuffer(s1);        StringBuffer sb2 = sb.reverse();        System.out.println("方法二反轉操作後為:" + sb2);        //利用倒序儲存實現反轉        String s3=myReverse(s1);        System.out.println("方法三反轉操作後為:" + s3);    }    public static String myReverse(String str)      {          char[] arr = new char[str.length()];          int pos = str.length();          for (int x=0; x<str.length(); x++)          {              arr[x] = str.charAt(--pos);          }          str = String.copyValueOf(arr);          return str;      }  }

輸出：

方法一反轉操作後為:fw gfed   cba方法二反轉操作後為:fw gfed   cba方法三反轉操作後為:fw gfed   cba

二、實現去字串兩端空格功能

package string;public class Trime {    public static void main(String[] args) {        String str1 = "   dwwg dwg  wfg   ";        //利用String類自己的方法去除兩端空格        String str2 = str1.trim();        System.err.println("方法一"+str2);        //自訂方法去除兩端空格        String str3=myTrim(str1);        System.err.println("方法二"+str3);    }    public static String myTrim(String str) {        int start = 0, end = str.length() - 1;        while (start <= end && str.charAt(start) == ' ')            start++;        while (start <= end && str.charAt(end) == ' ')            end--;        return str.substring(start, end + 1);    }}

輸出：

方法一dwwg dwg  wfg方法二dwwg dwg  wfg

三、擷取一個字串在另一個字串中出現的次數，並返回出現起始索引

package string;public class GetCount {    public static void main(String[] args) {        String str = "sshelloworldhellojavahellojsp";        System.out.println("count=" + getSubCount(str, "hello"));    }    public static int getSubCount(String str, String key) {        int count = 0;        int index = 0;        while ((index = str.indexOf(key, index)) != -1) {            System.out.println("index=" + index);            index = index + key.length();            count++;        }        return count;    }}

index=2index=12index=21count=3

indexOf返回的是長字串中所求子字串起始處索引值，沒有則返回-1.

四、將一段英文句子倒序輸出

package string;import java.util.Scanner;public class Reverse02 {    public static String reverseWords(String sentence) {        StringBuilder sb = new StringBuilder(sentence.length() + 1);        String[] words = sentence.split(" ");        for (int i = words.length - 1; i >= 0; i--) {            sb.append(words[i]).append(' ');        }        sb.setLength(sb.length() - 1);        return sb.toString();    }    public static void main(String[] args)    {        Scanner in = new Scanner(System.in);        // 存放輸入的字串        System.out.println("輸入測試案例數目n：");        String[] input = new String[in.nextInt()];        in.nextLine();        for (int i = 0; i < input.length; i++) {            input[i] = in.nextLine();        }        // 輸出倒序後的英文字串        System.out.println("輸出為：");        for (String s : input) {            System.out.println(reverseWords(s));        }    }}

輸入測試案例數目n：2hello world!i love you?輸出為：world! helloyou? love i

四、刪除一個字串中出現最多的字元

package string;import java.util.HashMap;import java.util.Map;import java.util.Set;public class DelMost {    public static void main(String[] args) {        String str = "aassdfscfw";        Map<Character, Integer> map = new HashMap<Character, Integer>();        char[] box = str.toCharArray();        for (char ch : box) {            Integer i = map.get(ch);            if (i == null) {                map.put(ch, 1);            } else {                map.put(ch, i + 1);            }        } // 建立map索引值對        Integer max = 0;        Set<Character> set = map.keySet();        for (Character key : set) {            Integer j = map.get(key);            if (max < j) {                max = j;            }        } // 將最大次數傳給max        for (Character key : set) {            if (map.get(key) == max) {                str = str.replaceAll(key.toString(), "");            }        }        System.out.println(str);    }}

aadfcfw

五、輸入一行字元分別統計英文字母、數字、空格個數。

package string;import java.util.Scanner;public class Tongji {    public static void main(String[] args) {        int eng=0,num=0,kong=0,elsel=0;        Scanner sc=new Scanner(System.in);        String str=sc.nextLine();        char[] ch=null;        ch=str.toCharArray();        for(char c:ch){            if(c>='0'&&c<='9'){                num++;            }else if((c>='a'&&c<='z')||(c>='A'&&c<='Z')){                eng++;            }else if(c==' '){                kong++;            }else{            elsel++;            }        }        System.out.println("字母有"+eng);        System.out.println("數字有"+num);        System.out.println("空格有"+kong);        System.out.println("其他"+elsel);    }}

hello world 378nihao字母有15數字有3空格有2其他0