比较并提取两个Hashmap

Question

I used Scanner to read through A.txt to generate A Hashmap, also same method to read through B.txt to have B Hashmap. These two hashmap have the "SOME" same key and would like to combine with each other. If the key is are the same, print out "key, value1, value2". Here is I have so far :

public static void main (String[] args) throws FileNotFoundException {
Scanner scanner1 = new Scanner(new File("score.txt"));
Map<String, String> tolerance = new HashMap<>();
Scanner scanner2 = new Scanner(new File("Count2.txt"));
Map<String, String> Pdegree = new HashMap<>();
while (scanner1.hasNextLine()) {
String line = scanner1.nextLine();
String[] array = line.split("\t",2);
String Name = array[0];
String score = array[1];
tolerance.put(Name,score);
}
while (scanner2.hasNextLine()) {
    String line2 = scanner2.nextLine();
    String[] array2 = line2.split("\t",2);
    String Name2 = array2[0];
    String degree = array2[1];
    Pdegree.put(Name2,degree);
    }
    for(Map.Entry<String, String> entry : tolerance.entrySet()) {
    String key = entry.getKey();
    String value = entry.getValue();
            for(Map.Entry<String, String> entry2 : Pdegree.entrySet()) {
            String key2 = entry2.getKey();
            String value2 = entry2.getValue();
            if(key==key2){
            System.out.println(key2 + "\t" + value + "\t" + value2);
            }
    }
 }
}
}

Neither results nor error messages would show. My question is how to extract the same key with respective values from two maps. Thanks.

Answer 1

I found the answer by myself. It should be

 if(key.equals(key2))

Answer 2

您可以使用map1.putAll(map2)合并两个地图；

Answer 3

Why not use Guava's multimap? I believe that if you use put all and it comes across two identical keys, it simply adds a second value to the key. Then you can print out all teh key value pairs. If it has identical key and identical value what it does is implementation dependent.

https://guava-libraries.googlecode.com/svn/tags/release03/javadoc/com/google/common/collect/Multimap.html#put(K , V)