Java学习-字符串练习

1.给出一句英文句子： "let there be light"
得到一个新的字符串，每个单词的首字母都转换为大写

知识点：split()，substring(start,end)，toUpperCase()，length()

 1 public class test {
 2     public static void main(String[] args) {
 3         String s = "let there be light";
 4         String[] s1 = s.split(" ");
 5         s = "";
 6         for (String x : s1) {
 7             x = x.substring(0, 1).toUpperCase() + x.substring(1, x.length()) + " ";
 8             s += x;
 9         }
10         s=s.trim();
11         System.out.println(s);
12     }
13 }

2.英文绕口令
peter piper picked a peck of pickled peppers
统计这段绕口令有多少个以p开头的单词

知识点：charAt()，spilt()

 1 public class test {
 2     public static void main(String[] args) {
 3         String s = "peter piper picked a peck of pickled peppers";
 4         int sum=0;
 5         for(String x:s.split(" "))
 6         {
 7             if(x.charAt(0)=='p')
 8                 sum++;
 9         }
10         System.out.printf("一共%d个",sum);
11     }
12 }

3.间隔大小写模式

把 lengendary 改成间隔大写小写模式，即 LeNgEnDaRy

知识点：toCharArray()，String.valueOf()，toUpperCase()

 1 public static void main(String[] args) {
 2         String s = "lengendary";
 3         char []cs=s.toCharArray();
 4         s="";
 5         for(int i=0;i<cs.length;i++){
 6             if((i+1)%2!=0){
 7                 s+=String.valueOf(cs[i]).toUpperCase();//char转String可以用String.valueOf(char)
 8             }
 9             else{
10                 s+=cs[i];
11             }
12         }
13         System.out.println(s);
14     }

4.把 lengendary 最后一个字母变大写

1     public static void main(String[] args) {
2         String s = "lengendary";
3         s=s.substring(0,s.length()-1)+s.substring(s.length()-1,s.length()).toUpperCase();
4         System.out.println(s);
5 
6     }

5.练习-把最后一个two单词首字母大写

Nature has given us that two ears, two eyes, and but one tongue, to the end that we should hear and see more than we speak

 1     public static void main(String[] args) {
 2         String s = "Nature has given us that two ears, two eyes, and but one tongue, to the end that we should hear and see more than we speak";
 3         int last_index_of_Two = s.lastIndexOf("two");
 4 
 5         String s1 = s.substring(0, last_index_of_Two);
 6         String keyWord = s.substring(last_index_of_Two, last_index_of_Two + 1).toUpperCase();
 7         String s2 = s.substring(last_index_of_Two + 1, s.length());
 8 
 9         s = s1 + keyWord + s2;
10         System.out.println(s);
11     }

6.比较字符串

PS：这题有点意思~

创建一个长度是100的字符串数组
使用长度是2的随机字符填充该字符串数组
统计这个字符串数组里重复的字符串有多少种

 1 package property;
 2 
 3 public class test {
 4     public static String randString(int n) {// 生成n位随机字符串
 5         String s = "";
 6         for (; n > 0; n--) {
 7             while (true) {
 8                 char c = (char) Math.round(Math.random() * 126);
 9                 if (Character.isLetter(c) || Character.isDigit(c)) {
10                     s += c;
11                     break;
12                 }
13             }
14         }
15         return s;
16     }
17 
18     public static void print(String s[])// 每行打印十个
19     {
20         int i;
21         for (i = 0; i < s.length; i++) {
22             if ((i + 1) % 10 != 0) {
23                 System.out.printf(s[i] + "\t");
24             } else {
25                 System.out.printf("%s\n", s[i]);
26             }
27         }
28     }
29 
30     public static void func(String s[]) {
31         String repS = "";
32         int sum = 0;
33         int judge[] = new int[100];// 辅助数组judge[]，标记重复过的字符串，judge[i]=1则遍历时跳过i
34         for (int i = 0; i < judge.length; i++) {// 初始化judge[]
35             judge[i] = 0;
36         }
37         int i, j, k;// i,j用来遍历，k用来记录最后一个相同的字符串的位置
38         for (i = 0; i < s.length && judge[i] == 0; i++) {
39             // judge[i] = 1;//可写可不写
40             int flag = 0;// 标记内层循环是否找到了相同的字符串，1：找到了
41             k = i;
42             for (j = i + 1; j < s.length && judge[j] == 0; j++) {
43 
44                 if (s[i].equals(s[j])) {
45                     judge[j] = 1;
46                     flag = 1;
47                     k = j;
48                 }
49             }
50             if (flag == 1) {
51                 sum++;
52                 repS += " " + s[k];
53             }
54         }
55         System.out.printf("一共有%d种重复字符串\n", sum);
56         if (sum != 0)
57             System.out.println("它们是：" + repS.trim());
58     }
59 
60     public static void main(String[] args) {
61 
62         String s[] = new String[100];
63         for (int i = 0; i < s.length; i++) {
64             s[i] = randString(2);
65         }
66         print(s);
67         func(s);
68 
69     }
70 }

运行结果：

Java学习-字符串练习

推荐阅读