Java 循环——每个单词的第一个和最后一个字符的字符串

Question

我目前正在圣何塞参加编程入门类(class)，作为作业的一部分，我们要创建一个类，其方法要么返回包含每个单词的第一个字母的字符串，要么返回每个单词的最后一个字母的字符串。

实例变量“phrase”保存在方法中访问的短语。

规则如下:

单词之间用空格分隔，它以一封信开头，它不以空格结尾，永远不会有 2 个连续的空格，永远不会有 2 个连续的数字或标点符号。

如果短语为空，则firstLetter() 和lastLetter() 方法都必须返回空字符串。

我的问题是:这个问题有什么更有效的解决方案？我对算法很陌生，所以我希望有更成熟的方法来解决这个简单的问题。在firstLetter()和lastLetter()方法中，我会在for循环中一次检查两个字符的状态还是只检查一个字符的状态？

这是我的代码:

/**
 * Processes first and last letters of words
 * @author (Adrian DeRose)
 */
public class StartToFinish
{
    private String phrase;

    /**
     * Constructs a StartToFinish object
     * @param myString the phase for this object
     */
     public StartToFinish(String myString)
     {
         this.phrase = myString;
     }

    /**
     * Gets first letter of every word in string. 
     * 
     * @return first letter of every word in string
     */
    public String firstLetters()
    {   
        String firstLetters = "";

        if (Character.isLetter(this.phrase.charAt(0)))
        {
            firstLetters += this.phrase.substring(0,1);
        }

        for (int i = 1; i < this.phrase.length(); i++)
        {
            char currentCharacter = this.phrase.charAt(i);
            String previousCharacter = Character.toString(this.phrase.charAt(i-1));
            if (Character.isLetter(currentCharacter) && previousCharacter.equals(" "))
            {
                String characterString = Character.toString(currentCharacter);
                firstLetters += characterString;
            }
        }
        return firstLetters;

    }

    /**
     * Gets last letter of every word in string. 
     * 
     * @return last letter of every word in string
     */
    public String lastLetters()
    {
        String lastLetters = "";
        char lastCharacter = this.phrase.charAt(lastIndex);

        if (this.phrase.length() == 0)
        {
            return "";
        }

        for (int i = 1; i < this.phrase.length(); i++)
        {
            char currentCharacter = this.phrase.charAt(i);
            char previousCharacter = this.phrase.charAt(i-1);

            if (Character.isLetter(previousCharacter) && !Character.isLetter(currentCharacter))
            {
                String previousCharacterString = Character.toString(previousCharacter);
                lastLetters += previousCharacterString;
            }
        } 

        if (Character.isLetter(lastCharacter))
        {
            lastLetters += Character.toString(lastCharacter);
        }

        return lastLetters;
    }
}

谢谢!

Answer 1

我不知道这是否是您正在寻找的内容，但这是编写相同内容的更简单的方法(抱歉我的英语)

String a="john snow winter is comming";
    String[] parts = a.split(" ");
    for(String word:parts){
        System.out.println("first letter "+word.charAt(0)+ " last letter "+word.charAt(word.length()-1));
    }