CODEWITHSUNDEEP
javahashmap
fuschia
fuschia

Reputation: 283

Get one of the values from Hashmap with multiple values

If I have a Hashmap as follows:

Hashmap<String, Node> nodeMap = new HashMap<String, Node>();

and Node stores multiple values consists of:

String name,
int year,
double weight

How can I print out one of the multiple values stored in this hashmap? I actually have no idea to just print one of the value (which is what I need the most) But as a start, I tried to print all the values first by using following query

Set<String> keySet= nodeMap.keySet();
    for(String x:keySet){
        System.out.println(nodeMap.get(x));
    }

However, I got an output for example like Node@73a28541, Node@6f75e721, Node@69222c14.

I am trying to get the real value of like what is the name, what year, and what is the weight of each key in the Hashmap but it is still not working yet.

And I actually need to know how to print just one of the value..

Any help would be really appreciated. Thank you

EDIT: This is how I stored the Hashmap and node value:

Node n = new Node(resultSet.getString(1), resultSet.getInt(2),weight);
               nodeMap.put(resultSet.getString(1),n);

My expected output is that if I have a certain key for example 123, I want to get the year value of the 123 key.

Upvotes: 0

Views: 3081

Answers (4)

Stephan
Stephan

Reputation: 43013

Since the nodeMap.get method is called, the entrySet method should be use instead of keySet.

Here is a little comparison of the use of the two methods:

// Create Map instance and populate it
Map<String, Node> nodeMap = new HashMap<String, Node>();
for (int i = 0; i < 100; i++) {
    String tmp = Integer.toString(i);
    nodeMap.put(tmp, new Node(tmp, 2015, 3.0));
}

// Test 1: keySet + get
long t1 = System.nanoTime();
for (String x : nodeMap.keySet()) {
    nodeMap.get(x);
}
System.out.format("keySet + get: %d ns\n" , System.nanoTime() - t1);

// Test 2: entrySet + getValue
t1 = System.nanoTime();
for (Map.Entry<String, Node> e : nodeMap.entrySet()) {
    e.getValue();
}
System.out.format("entrySet + getValue: %d ns\n" , System.nanoTime() - t1);

Output

keySet + get: 384464 ns
entrySet + getValue: 118813 ns

I ran repeatedly this test. On average, entrySet + getValue is twice faster than keySet + get.

Upvotes: 1

Rahul Parida
Rahul Parida

Reputation: 175

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

public class TestMap {
    static class Node {
        public String name;
        public int year;
        public double weight;

        public Node(String name, int year, double weight) {
            this.name = name;
            this.year = year;
            this.weight = weight;
        }

        @Override
        public String toString() {
            // here you can create your own representation of the object
            String repr = "Name:" + name + ",year:" + year + ",weight:" + weight;
            return repr;
            }
        }

    public static void main(String args[]) {
        Map<String, Node> map = new HashMap<String, Node>();
        Node node1 = new Node("A",1987,70.2);
        Node node2 = new Node("B", 2014, 66.4);
        String key1 = "123";
        String key2 = "345";
        map.put(key1,node1);
        map.put(key2,node2);

        Set<String> keySet= map.keySet();
        for(String x:keySet){
            System.out.println(map.get(x));
        }

       System.out.println(map.get(key1).name); 
    }
}

The code above should explain it all.

Upvotes: 3

MadConan
MadConan

Reputation: 3767

for(String key : keySet){
   Node n = map.get(key);
   System.out.println(n.getYear());
}

Upvotes: 1

Eyal
Eyal

Reputation: 1768

In the class Node, override the function toString which will be called when printing a node, you can choose how the printing will appear.

Upvotes: 2

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