public static String firstUpper(String str) {
		String[] strs = str.split(" ");
		String target = "";
		for (int i = 0; i < strs.length; i++) {
			char[] temp = strs[i].toCharArray();
			temp[0] = Character.toUpperCase(temp[0]);
			if (i > 0)
				target += " ";
			target += (new String(temp));
		}
		return target;
	}

	public static int getBeginLetterNumber(String str, char letter) {
		String[] strs = str.split(" ");
		int count = 0;
		for (int i = 0; i < strs.length; i++) {
			char[] temp = strs[i].toCharArray();
			if (temp[0] == letter)
				count++;
		}
		return count;
	}

	public static String intervalConversion(String str) {
		char[] temp = str.toCharArray();
		for (int i = 0; i < temp.length; i++) {
			if ((i % 2) == 0)
				temp[i] = Character.toUpperCase(temp[i]);
			else
				temp[i] = Character.toLowerCase(temp[i]);
		}
		return new String(temp);
	}

	public static String latLetterUpper(String str) {
		String[] strs = str.split(" ");
		String target = "";
		for (int i = 0; i < strs.length; i++) {
			char[] temp = strs[i].toCharArray();
			temp[temp.length - 1] = Character.toUpperCase(temp[temp.length - 1]);
			if (i > 0)
				target += " ";
			target += (new String(temp));
		}
		return target;
	}

	public static String sLastLetterUpper(String str, String target) {
		int index = str.lastIndexOf(target);
		char[] temp = str.toCharArray();
		temp[index] = Character.toUpperCase(temp[index]);
		return new String(temp);
	}

	public static void main(String[] args) {
		System.out.println("1.-----------------------------------------------");
		String english = "let there be light.";
		String formatHint = "将下列句子每个单词首字母大写%n%s%n变更后%n%s%n";
		System.out.format(formatHint, english, firstUpper(english));
		System.out.println("2.-----------------------------------------------");
		String english2 = "peter piper picked a peck of pickled peppers";
		String formatHint2 = "统计下列句子单词中，字母'%c'开头单词数量%n%s%n统计数量: %d%n";
		int number = getBeginLetterNumber(english2, 'p');
		System.out.format(formatHint2, 'p', english2, number);
		System.out.println("3.-----------------------------------------------");
		String english3 = "lengendary";
		String formatHint3 = "将下列句子变更大小写模式%n%s%n变更后%n%s%n";
		System.out.format(formatHint3, english3, intervalConversion(english3));
		System.out.println("4.-----------------------------------------------");
		String english4 = "lengendary ";
		String formatHint4 = "将下列单词最后一个字母变更为大写%n%s%n变更后%n%s%n";
		System.out.format(formatHint4, english4, latLetterUpper(english4));
		System.out.println("5.-----------------------------------------------");
		String english5 = "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.";
		String formatHint5 = "将下列句子最后一个'%s'单词的首字母大写%n%s%n变更后%n%s%n";
		System.out.format(formatHint5, "two", english5, sLastLetterUpper(english5, "two"));

	}

import java.util.*;
public class str{ 
    public static void main(String[] args) {
        String title="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";
        char[]tc=title.toCharArray();
        for(int i=0;i<3;i++){
        tc[title.lastIndexOf("two")+i]=Character.toUpperCase(tc[title.lastIndexOf("two")+i]);
        }
        
        System.out.println(tc);
}
}

			String str =  "peter piper picked a peck of pickled peppers";	//题目
			System.out.println( str.split(" p").length );                                //解出答案，分隔后统计长度

        //练习-3
        //间隔大写小写模式
        //把 lengendary 改成间隔大写小写模式，即 LeNgEnDaRy
        String str3 = "lengendary";
        String arr3[] = str3.split("");
        for (int i = 0; i < arr3.length; i++) {
            if (i%2 == 0){
                arr3[i] = arr3[i].toUpperCase();
            }
        }
        str3 = String.join("", arr3);
        System.out.printf("str3: %s%n", str3);

package how2j._1_Java基础._8_数字与字符串;

import java.util.Arrays;
public class _7_Manipulating_a_string {
    public static void main(String[] args){

        //练习-1
        //每个单词的首字母都转换为大写
        //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
        String str = "let there be light";
        String []arr = str.split(" ");
        for(int i=0;i<arr.length;i++){
            arr[i]=arr[i].replace(arr[i].charAt(0),arr[i].toUpperCase().charAt(0));
        }
        System.out.println(Arrays.toString(arr));


        //练习-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
        String str2 = "peter piper picked a peck of pickled peppers";
        String []arr2 = str2.split(" ");
        int count=0;
        for(String i : arr2){
            if(String.valueOf(i.charAt(0)).equals("p")){
                count+=1;
            }
        }
        System.out.println(count);

        //练习-3
        //间隔大写小写模式
        //把 lengendary 改成间隔大写小写模式，即 LeNgEnDaRy
        String str3 = "lengendary";
        String []arr3 = str3.split("");
        String str4="";
        for(int i=0;i<arr3.length;i++){
            if(i%2==0){//下标从0开始
                str4+=arr3[i].toUpperCase().charAt(0);
            }else{
                str4+=arr3[i];
            }
        }
        System.out.println(str4);

        //练习-4
        //最后一个字母变大写
        //把  最后一个字母变大写
        String str5 ="lengendary";
        str5=str5.replace(str5.charAt(str5.length()-1),str5.toUpperCase().charAt(str5.length()-1));
        System.out.println(str5);

        //练习-5
        //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
        //把最后一个two单词首字母大写
        String str6="Nature has given us that two ears,two eyes, two and two but one tongue, to the end that we should hear and see more than we speak";
        String str7=reverse(str6);
        str7=str7.replaceFirst("two","Two");
        String str8=reverse(str7);
        System.out.println(str8);
    }
    public static String reverse(String str){
        String str2="";
        String []arr = str.split(" ");
        for (int i= arr.length-1;i>=0;i--){
            str2+=arr[i]+" ";
        }
        return str2;
    }
}