java - 检查元素是否已经在Java数组中

我现在正在从事的项目涉及到我从文本文件中读取单词并将它们加载到数组中（最终是一个二叉树，但这将在以后完成）。我必须将单词和单词的频率（最初为1）加载到数组中，因此我已经将两个变量都打包到对象WordNode中。我能够将单词加载到数组中，但是当我尝试检查单词是否已在数组中时，事情就崩溃了。如果是这样，我必须将频率增加1。但是，我的代码甚至不检查单词，而只是添加它（我想它是在检查对变量的引用，而不是单词本身）。下面是我的main方法和WordNode类。

主要方法：

public class Driver {
/////////////// fields ///////////////
public static ArrayUnorderedList<WordNode> wordArray = new ArrayUnorderedList<WordNode>();
public static LinkedBinarySearchTree<WordNode> wordTree = new LinkedBinarySearchTree<WordNode>();   //tree to hold words

/////////////// methods ///////////////
public static void main(String[] args) throws Exception {
    //ask for filename
    BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    System.out.println("Enter the name of the file to read from: ");
    Reader file = new FileReader(reader.readLine());

    //read file
    Scanner input = new Scanner(file);

    while(input.hasNext()) {
        //get words from file
        String word = input.next();

        //remove non-word characters and convert to lowercase
        word = word.replaceAll("\\W", "");
        word = word.toLowerCase();

        //create node
        WordNode newWord = new WordNode(word);

        //if word is already in array
        if(wordArray.contains(newWord)) {
            System.out.println("Word is already in array");

            //increment frequency by 1
            int index = wordArray.find(newWord);
            wordArray.list[index].setFrequency(wordArray.list[index].getFrequency() + 1);
            System.out.println(newWord.getWord() + newWord.getFrequency());
        } else {
            System.out.println("Word is not yet in array");

            //add word to tree
            System.out.println(newWord.getWord());
            wordArray.addToRear(newWord);
        }
    }

    //insert into tree

    //perform traversals on tree
}

WordNode类：

public class WordNode {
   protected String word;
   protected WordNode left, right;
   protected int frequency;

   /**
    * Creates a new node with the specified data.
    * @param obj the element that will become a part of the new node
    */
   WordNode(String obj) {
      word = obj;
      left = null;
      right = null;
      frequency = 1;
   }

   /**
    * Gets the word.
    * @return the word
    */
   public String getWord() {
      return word;
   }

   /**
    * Sets the word.
    * @param word the word to set
    */
   public void setWord(String word) {
      this.word = word;
   }

   /**
    * Gets the left.
    * @return the left
    */
   public WordNode getLeft() {
      return left;
   }

   /**
    * Sets the left.
    * @param left the left to set
    */
   public void setLeft(WordNode left) {
      this.left = left;
   }

   /**
    * Gets the right.
    * @return the right
    */
   public WordNode getRight() {
      return right;
   }

   /**
    * Sets the right.
    * @param right the right to set
    */
   public void setRight(WordNode right) {
      this.right = right;
   }

   /**
    * Gets the frequency.
    * @return the frequency
    */
   public int getFrequency() {
      return frequency;
   }

   /**
    * Sets the frequency.
    * @param frequency the frequency to set
    */
   public void setFrequency(int frequency) {
      this.frequency = frequency;
   }
}

ArrayList类中的一些方法：

/**
* Returns true if this list contains the specified element.
* @param target the element that the list is searched for
* @return true if the target is in the list, false if otherwise
*/
public boolean contains(T target) {
    return (find(target) != NOT_FOUND);
}

/**
* Returns the array index of the specified element, or the
* constant NOT_FOUND if it is not found.
* @param target the element that the list will be searched for
* @return the integer index into the array containing the target element, or the NOT_FOUND constant
*/
public int find(T target) {
    int scan = 0, result = NOT_FOUND;
    boolean found = false;

    if (!isEmpty()) {
       while (!found && scan < rear) {
          if (target.equals(list[scan])) {
              found = true;
          } else {
             scan++;
          }
       }
    }

    if (found) {
       result = scan;
    }

    return result;
}

最佳答案

您的代码不起作用的直接原因是ArrayUnorderedList#contains()可能依赖equals()方法来确定条目是否在列表中。如果没有看到类的定义，就不可能知道。

由于未提供equals()的替代，因此它使用对象标识（Object的默认值），因此每个WordNode与其他WordNode都不同。

如果要使用ArrayUnorderedList，则必须以正确的行为实现WordNode#equals()。

但是，您应该考虑使用Map<String,Integer>（或Map<String,WordNode>）存储频率。这样会更快。