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()

public class test {
    public static void main(String[] args) {
        String s = "let there be light";
        String[] s1 = s.split(" ");
        s = "";
        for (String x : s1) {
            x = x.substring(0, 1).toUpperCase() + x.substring(1, x.length()) + " ";
            s += x;
        }
        s=s.trim();
        System.out.println(s);
    }
}

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()

public class test {
    public static void main(String[] args) {
        String s = "peter piper picked a peck of pickled peppers";
        int sum=0;
        for(String x:s.split(" "))
        {
            if(x.charAt(0)=='p')
                sum++;
        }
        System.out.printf("一共%d个",sum);
    }
}

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()

public static void main(String[] args) {
        String s = "lengendary";
        char []cs=s.toCharArray();
        s="";
        for(int i=0;i<cs.length;i++){
            if((i+1)%2!=0){
                s+=String.valueOf(cs[i]).toUpperCase();//char转String可以用String.valueOf(char)
            }
            else{
                s+=cs[i];
            }
        }
        System.out.println(s);
    }

4.把 lengendary 最后一个字母变大写

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

    }

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

    public static void main(String[] args) {
        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";
        int last_index_of_Two = s.lastIndexOf("two");

        String s1 = s.substring(0, last_index_of_Two);
        String keyWord = s.substring(last_index_of_Two, last_index_of_Two + 1).toUpperCase();
        String s2 = s.substring(last_index_of_Two + 1, s.length());

        s = s1 + keyWord + s2;
        System.out.println(s);
    }

 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

package property;

public class test {
    public static String randString(int n) {// 生成n位随机字符串
        String s = "";
        for (; n > 0; n--) {
            while (true) {
                char c = (char) Math.round(Math.random() * 126);
                if (Character.isLetter(c) || Character.isDigit(c)) {
                    s += c;
                    break;
                }
            }
        }
        return s;
    }

    public static void print(String s[])// 每行打印十个
    {
        int i;
        for (i = 0; i < s.length; i++) {
            if ((i + 1) % 10 != 0) {
                System.out.printf(s[i] + "	");
            } else {
                System.out.printf("%s
", s[i]);
            }
        }
    }

    public static void func(String s[]) {
        String repS = "";
        int sum = 0;
        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
        for (int i = 0; i < judge.length; i++) {// 初始化judge[]
            judge[i] = 0;
        }
        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
        for (i = 0; i < s.length && judge[i] == 0; i++) {
            // judge[i] = 1;//可写可不写
            int flag = 0;// 标记内层循环是否找到了相同的字符串，1：找到了
            k = i;
            for (j = i + 1; j < s.length && judge[j] == 0; j++) {

                if (s[i].equals(s[j])) {
                    judge[j] = 1;
                    flag = 1;
                    k = j;
                }
            }
            if (flag == 1) {
                sum++;
                repS += " " + s[k];
            }
        }
        System.out.printf("一共有%d种重复字符串
", sum);
        if (sum != 0)
            System.out.println("它们是：" + repS.trim());
    }

    public static void main(String[] args) {

        String s[] = new String[100];
        for (int i = 0; i < s.length; i++) {
            s[i] = randString(2);
        }
        print(s);
        func(s);

    }
}

运行结果：