如何在Java中使用地图迭代地图

Question

我有以下代码：

/*
if inputDetailsMap has values like:
String      String
 key1       value1
 key2       value2
 key3       value3
 key4       value4
 key5       value5
so on.....
*/

public void inputData(Map<String,String> inputDetailsMap, String fileName){
    //a for loop to run
          String value = inputDetailsMap.get("key" + i);    // i value comes from the for loop
          //i am doing something with the value.
    //end of for loop
}

如果我想遍历Map，上面的代码效果很好。 但是现在我有这样的事情。

/*
inputDetailsMap has values like:
int         String      String
 1           key1       value1
             key2       value2
             key3       value3
             key4       value4
             key5       value5
 2           key1       value1
             key2       value2
             key3       value3
             key4       value4
             key5       value5
so on.....
*/
 public void inputData(Map<Integer,Map<String,String>> inputDetailsMap, String fileName){
      //how to iterate and get the value using inputDetailsMap.get() like the above code??
}

我想遍历Map中的Map并获取其键和值。 我想获取key1，value1，key2，value2，key3，value3等的值。 那我该怎么办呢？

Answer 1

您可以使用：

String value = inputDetailsMap.get(1).get("key" + i);

第一次获取将获得正确的Map<String, String> （对于键1或2）。

第二次获得将获得正确的值（对于key1，key2 ...）

Answer 2

public void inputData(Map<Integer,Map<String,String>> inputDetailsMap) {
    for (Map.Entry<Integer, Map<String,String> entry : inputDetailsMap.entrySet()) {            
        Map<String, String>innerMap = entry.getValue()
        for (Map.Entry<String, String> keyPair : innerMap.entrySet()) {
            String key = keyPair.getKey();
            String value = keyPair.getValue();
            // do something with value
        }
    }
}

Answer 3

您可能最好看一下Guava的Multimap：

http://tomjefferys.blogspot.co.uk/2011/09/multimaps-google-guava.html

http://guava-libraries.googlecode.com/svn-history/r14/trunk/javadoc/com/google/common/collect/Multimap.html

但是不使用它：

import java.util.HashMap;
import java.util.Map;

 public class MapInMap {

public static void main(String[] args){

    for (Integer index: outerMap.keySet()){
        for (String innerIndex: outerMap.get(index).keySet()){
            System.out.println(String.format("%s :: %s :: %s", index, innerIndex, outerMap.get(index).get(innerIndex)));
        }
    }

}

/*
inputDetailsMap has values like:
int         String      String
 1           key1       value1
             key2       value2
             key3       value3
             key4       value4
             key5       value5
 2           key1       value1
             key2       value2
             key3       value3
             key4       value4
            key5       value5
so on.....
*/
static Map<String, String> innerMap1 = new HashMap<String, String>(){{
    put("key1", "value1");
    put("key2", "value2");
    put("key3", "value3");
    put("key4", "value4");
    put("key5", "value5");
}};
static Map<String, String> innerMap2 = new HashMap<String, String>(){{
    put("key1", "value1");
    put("key2", "value2");
    put("key3", "value3");
    put("key4", "value4");
    put("key5", "value5");
}};

static Map<Integer, Map<String,String>> outerMap = new HashMap<Integer, Map<String,String>>(){{
    put(1, innerMap1);
    put(2, innerMap2);
}};
}

Answer 4

尝试这个

public void inputData(Map<int,Map<String,String>> inputDetailsMap, String fileName){
    System.out.println(inputDetailsMap.get(fileName));
}