我如何在 Java 中使用字符串反转大写和逐行分隔单词？

Question

The input is: i love cake

The output needs to be: Cake Love I

But the actual result is: I Love Cake

What I've got:

import java.util.regex.Pattern; 
public class yellow {

    static String reverseWords(String str){
        Pattern pattern = Pattern.compile("\\s");
        String[] temp = pattern.split(str);
        String result = "";

        for (int i = 0; i < temp.length; i++) {
            if (i == temp.length - 1)
                result = temp[i] + result;
            else
                result = " " + temp[i] + result;
        }
        return result;
    }

    public static void main(String[] args){
        String source = "i love cake";
        StringBuffer res = new StringBuffer();

        String[] strArr = source.split(" ");
        for (String str : strArr) {
            char[] stringArray = str.trim().toCharArray();
            stringArray[0] = Character.toUpperCase(stringArray[0]);
            str = new String(stringArray);

            res.append(str).append(" ");
        }
        System.out.print(res.toString());
    }
}

What am I doing wrong?

Answer 1

for (String str : strArr) {

}

This loops forward. What you want is to loop backwards, or to place elements into the string backwards. I recommend you loop backwards and print as you go:

for (int i = strArr.length - 1; i >= 0; i--) {
    char[] stringArray = strArr[i].trim().toCharArray();
    stringArray[0] = Character.toUpperCase(stringArray[0]);
    System.out.println(new String(stringArray));
}

Or, you could use that convenient reverseWords method that you never use anywhere... though looping backwards is faster. Probably.

Answer 2

[EDITED] Call this for each line with string s, then print a line break (If you have multiple sentences & expect them in their own lines).

void reverseCamel(String s){
    String[] ar = s.split("\\s+");
    for(int i = ar.length - 1;i>=0;i--){
        ar[i][0] = Character.toUpperCase(ar[i][0]);
        System.out.print(ar[i] + " ");
    }
}

Answer 3

Here is what i did.

public class Main {

public static void main(String[] args) {
    reverse("I Love Cake");
}

public static void reverse( String string){
    String[] word =string.split(" "); // split by spaces
    int i = word.length-1;
    while (i>=0){
       // System.out.print(word[i].toUpperCase()+" ");//if you want in upper case
        System.out.print(word[i]+" ");
        i--;
      }
   }
}

Answer 4

First of all you have to reverse the String.

String[] words = source.split("\\s");
String reversedString = "";
for(int i = words.length -1; i>=0; i--){
    reversedString += words[i] + " ";
}

Then, you know that the ASCII code of 'a' character is 97, 'A' is 65. To convert from lower case to capital you substract 32. All capitals are between 65 and 92. All small letters are between 97 and 124. You want to capitalize only letters at the beginning of a word (preceded by a space or first letter).

String capitalCase = "";
        for (int i = 0; i < reversedString.length(); i++) {
            char c = reversedString.charAt(i);
            if (c >= 97 && c <= 124) {
                if (i == 0) c -= 32;
                else if ((reversedString.charAt(i - 1) + "").equals(" ")) c -= 32;
            }
            capitalCase += c;
        }

And here you go now System.out.println(capitalCase);

Overall, you will have the following code:

import java.util.Scanner;

public class yellow {
    public static void main(String[] args) {

        Scanner s = new Scanner(System.in);
        System.out.println("Enter a string:");
        String source = s.nextLine();

        String[] words = source.split("\\s");
        String reversedString = "";
        for (int i = words.length - 1; i >= 0; i--) {
            reversedString += words[i] + " ";
        }

        String capitalCase = "";
        for (int i = 0; i < reversedString.length(); i++) {
            char c = reversedString.charAt(i);
            if (c >= 97 && c <= 124) {
                if (i == 0) c -= 32;
                else if ((reversedString.charAt(i - 1) + "").equals(" ")) c -= 32;
            }
            capitalCase += c;
        }

        System.out.println(capitalCase);
    }
}

Output:

Enter a string:
i love cake
Cake Love I 

Answer 5

Java 8 * Apache Commons Lang

public static String reverseWordsInString(String str) {
    List<String> words = Pattern.compile("\\s+").splitAsStream(str)
                                .map(StringUtils::capitalize)
                                .collect(LinkedList::new, LinkedList::addFirst, (a, b) -> a.addAll(0, b));
    return words.stream().collect(Collectors.joining(StringUtils.SPACE));
}

Java 8

public static String reverseWordsInString(String str) {
    List<String> words = Pattern.compile("\\s+").splitAsStream(str)
                                .map(word -> Character.toUpperCase(word.charAt(0)) + word.substring(1).toLowerCase())
                                .collect(LinkedList::new, LinkedList::addFirst, (a, b) -> a.addAll(0, b));
    return words.stream().collect(Collectors.joining(" "));
}