使用add，remove和contains方法实现数据结构

Question

I would like to create a data structure in java, basically I have researched this and the best structure would be a list to allow for duplicates, I would like to attempt this without the Java API. I don't know how to go about doing this or even starting this and have already done around 6 hours of research.

class WordStoringTest implements WordStore {
    private String[] words;

    public WordStoringTest(int n){
        words = new String[n];
    }
    public void add(String word) {
        int count = words.length+1;
        words = new String[count];
    }

    @Override
    public int count(String word) {
    int count =0;
        for(int i=0; i<words.length; i++){
            if(words[i].equals(word)){
                count++;
            }
        }
        return count;
    }

    @Override
    public void remove(String word) {
        // TODO Auto-generated method stub
    }
}

I don't know where to start please give me some guidance :) thanks

Answer 1

There are inconsistencies in your code that make understanding it quite hard.... for example, you suggest a 'set' is the thing you want it to be, but then you have a count(...) method which indicates you expect multiple copies of the values in the 'set'. Traditional understanding is that members of a 'set' are not equals() to any other member of the set.

Additionally, what you have right now is just an array of data. This data array does not give you any advantages.... Things that would be advantages are (the sorts of things you get in java.util.*):

• all values are unique
• the ability to search the data is 'fast'
• there is reduced maintenance because the data will grow/shrink as you need it.
• the data is always sorted

... something has to be better than just a plain array.

Right now, not even you add() method works:

public void add(String word) {
    int count = words.length+1;
    words = new String[count];
}

The above method will delete all the data in the array by creating an empty one, and that's all.

My suggestion os for you to look through some standard examples for how things are done... consider looking at .... google basic java data structures .... I found this blog which looks useful

Answer 2

How about this (Tested).

Note: This is like a Java List, NOT Set because there are duplicate.

This is not the best implementation. We can prepare array buffer for word array like initialCapacity.

public class WordStoringTest implements WordStore {

private String[] words;

public WordStoringTest() {
    this(0);
}

public WordStoringTest(int n) {
    this.words = new String[n];
}

public void add(String word) {
    String[] newWords = new String[this.words.length + 1];
    System.arraycopy(this.words, 0, newWords, 0, this.words.length);
    newWords[newWords.length - 1] = word;
    this.words = newWords;
}

// @Override
public int count(String word) {
    int count = 0;
    for (String w : this.words) {
        if (word.equals(w)) {
            count++;
        }
    }
    return count;
}

// @Override
public void remove(String word) {
    int pos = 0;
    String[] temp = this.words;
    while (pos < temp.length) {
        String w = temp[pos];
        if (w.equals(word)) {
            String[] newTemp = new String[temp.length - 1];
            if (pos == 0) {
                System.arraycopy(temp, 1, newTemp, 0, newTemp.length);
            } else if (pos == temp.length - 1) {
                System.arraycopy(temp, 0, newTemp, 0, newTemp.length);
            } else {
                System.arraycopy(temp, 0, newTemp, 0, pos);
                System.arraycopy(temp, pos + 1, newTemp, pos, newTemp.length - pos);
            }
            temp = newTemp;
        } else {
            pos++;
        }
    }
    this.words = temp;
}

}