计算字符串中存在的单词

给定一个单词数组和一个字符串，我们需要计算给定字符串中出现的所有单词。

例子：

Input : words[] = { "welcome", "to", "geeks", "portal"}
            str = "geeksforgeeks is a computer science portal for geeks."
Output :  2
Two words "portal" and "geeks" is present in str.


Input : words[] = {"Save", "Water", "Save", "Yourself"}
        str     = "Save"
Output :1

脚步：

1. 从字符串中提取每个单词。
2. 对于每个单词，检查它是否在单词数组中（通过创建集合/映射）。如果存在，则增加结果。

下面是上述步骤的Java实现

// Java program to count number 
// of words present in a string
  
import java.util.HashSet;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
  
public class Test 
{
    static int countOccurrence(String[] word, String str) 
    {
        // counter
        int counter = 0;
          
        // for extracting words
        Pattern p = Pattern.compile("[a-zA-Z]+");
        Matcher m = p.matcher(str);
          
        // HashSet for quick check whether
        //  a word in str present in word[] or not
        HashSet hs = new HashSet();
          
        for (String string : word) {
            hs.add(string);
        }
          
        while(m.find())
        {
            if(hs.contains(m.group()))
                counter++;
        }
          
        return counter;
          
    }
      
    public static void main(String[] args) 
    {
        String word[] = { "welcome", "to", "geeks", "portal"};
          
        String str = "geeksforgeeks is a computer science portal for geeks.";
          
        System.out.println(countOccurrence(word,str));
          
    }
  
}

输出：

2