Question

这是我的代码，我似乎无法让差异方法正常工作当我尝试查看是否！other.contains（set）时我得到一个错误，当我在检查它是否包含后尝试添加它时相同它。不知道我需要做些什么才能修复它，但是如果有人可以提供帮助那就太棒了。

private ArrayList<String> set = new ArrayList<String>();


public boolean add(String word)
{

boolean x = true;
    if (word == null || word == "")
    {
        x = false;
    } else
    {
        if (word.length() > 0)
        {
            set.add(word);
            x = true;
            size++;
        }
    }
    return x;
}

public boolean contains(String word)
{

    boolean contains = false;
    if (word != null)
        contains = set.contains(word);
    return contains;
}


 /**
 * WordSet - This method should return a WordSet containing the words that
 *are in the current set but not in the other set (this – other).
 * 
 * @param other
 * @return WordSet
 */

public WordSet difference(WordSet other)
{
    WordSet differenceSet = new WordSet();
    boolean x = false;
    if (other != null)
        for (String str : set)
            if (!other.contains(set))
                differenceSet.add(set);
            return differenceSet;
}

Answer 1

您需要检查 null 条件。
if (null != other.contains(set) && !other.contains(set)){ //your code here }

或者我认为你可能想检查 str 而不是_set_the只需将它替换为contains（）

if (word != null) contains = set.contains(word); return contains; // -> this will return null if contains is null which is causing the second error
在这里应用类似的补丁

if (word != null) {
if(null != set.contains(word) { contains = set.contains(word);
}
}
return contains;

Answer 2

你的问题不是很清楚但我想下面是你的代码的问题。

public WordSet difference(WordSet other)
{
  WordSet differenceSet = new WordSet();
  boolean x = false;
  if (other != null)
      for (String str : set)
          {   
         if (!other.contains(str)) // You need to match with string in the set not the set.
             differenceSet.add(set);
          }
         return differenceSet;
}

使用数组列表并获取错误

2 个答案: