Java String類練習題

標籤：

題目：
1. 給定一個字串,判斷該字串中是否包含某個子串.如果包含,求出子串的所有出現位置.
如:"abcbcbabcb34bcbd"中,"bcb"子串的出現位置為: 1,7,12.字串和子串均由使用者輸入

2.給定一個長度,隨機產生一個該長度的字串,由大寫,小寫字母以及數字組成
Java中隨機數的產生:
java.util.Random r = new java.util.Random();
int a = r.nextInt(100): a 0-99的隨機數

3.給定一個由數字組成的字串,如:"1239586838923173478943890234092",統計
出每個數字出現的次數

答案如下：

package Chp10;import java.util.HashMap;import java.util.Map;import java.util.Random;import java.util.Scanner;import java.util.Set;public class TestString2{public static void Method_One(){Scanner s = new Scanner(System.in);System.out.println("請輸入一個父串");String str = s.next();System.out.println("請輸入一個子串");String str1 = s.next();int stat = 0;while (true){int i = str.indexOf(str1,stat);if (i==-1){break;}System.out.println(i);stat = i+str1.length();}}public static void Method_Two(){System.out.println("請輸入一個長度");Scanner s = new Scanner(System.in);int n = s.nextInt();char[] cs = new char[n];Random random = new Random();for (int i = 0; i < n; i++){int a = random.nextInt(62);if(a>=0 && a<=25){a+=65;}else if (a>25 && a<=51) {// 97 - 26 = 71a+=71;}else {// 52-48 = 4a-=4;}cs[i] = (char)a;}System.out.println(cs);}public  static void  Method_Three(){Scanner scanner = new Scanner(System.in);String string = scanner.next();int[] c = new int[10];for (int i = 0; i < string.length(); i++){char c1 = string.charAt(i); //48-57int a = c1-48;// 類型轉換c[a]++;}for (int i = 0; i < c.length; i++){System.out.println(i+" 出現的次數： "+c[i]);}System.out.println("=========方法二==========");String s = "12548954231351486214894562";char[] ch = s.toCharArray();Map<Character, Integer> map = new HashMap<Character, Integer>();Set<Character> set = map.keySet();for (int i = 0; i < ch.length; i++){if (set.contains(ch[i])) // 判斷map中已經有的char值{map.put(ch[i], map.get(ch[i])+1);} else{map.put(ch[i], 1); // 第一次放入map中}}Set<Character> set2 = map.keySet();for (Character character : set2){System.out.println(character+"=========="+map.get(character));}}public static void main(String[] args){System.out.println("第一題如下:");Method_One();System.out.println("第二題如下:");Method_Two();System.out.println("第三題如下:");Method_Three();}}

　　

　　

Java String類練習題