CODEWITHSUNDEEP
javaforeachhashmap
Sarath S Nair
Sarath S Nair

Reputation: 613

How to convert HashMap.getKey() to Int

I have a HashMap which stores Attendance information. I just want to convert the Key to Int and check for condition.

Below is my code:

import java.util.*;

public class HashClass {

    public static void main(String args[]) {

        HashMap<Integer, String> attendanceHashMap = new HashMap<Integer, String>();
        attendanceHashMap.put(1, "John");
        attendanceHashMap.put(2, "Jacob");
        attendanceHashMap.put(3, "Peter");
        attendanceHashMap.put(4, "Clara");
        attendanceHashMap.put(5, "Philip");

        for(HashMap.Entry m:attendanceHashMap.entrySet()){
            if(Integer.valueOf((int)m.getKey())<3) break;
            System.out.println(m.getKey()+" "+m.getValue());
        }
    }
}

I want to print like this

3 Peter
4 Clara
5 Philip

I tried these methods:

 - (int)m.getKey() : not working
 - Integer.valueOf((int)m.getKey()) : not working
 - Integer.valueOf(m.getKey()) : not working

How this can be achieved ?

Upvotes: 2

Views: 15411

Answers (3)

4862610
4862610

Reputation: 325

you mean you dont want to show the entries which key < 3 ,I think when you run this code you will get nothing because when key = 1 ,key < 3 = true and the loop break, they won`t continue you can try continue instead of break

Upvotes: 0

Holger
Holger

Reputation: 298143

You are saying:

if(Integer.valueOf((int)m.getKey())<3) break;

In other words, if the first key you encounter happens to be smaller than three, you terminate the loop, hence print nothing. Most probably, you want to use continue instead, to process the next entry:

for(HashMap.Entry m:attendanceHashMap.entrySet()){
    if(Integer.valueOf((int)m.getKey())<3) continue;
    System.out.println(m.getKey()+" "+m.getValue());
}

But note that the type conversions are obsolete. Just add the missing type arguments to the entry:

for(HashMap.Entry<Integer,String> m:attendanceHashMap.entrySet()){
    if(m.getKey()<3) continue;
    System.out.println(m.getKey()+" "+m.getValue());
}

But it might be clearer to make the print statement conditional instead of using loop control:

for(HashMap.Entry<Integer,String> m:attendanceHashMap.entrySet()){
    if(m.getKey()>=3) {
        System.out.println(m.getKey()+" "+m.getValue());
    }
}

As a side note, the order of the printed entries is not guaranteed. If you want to print the entries in insertion order, use a LinkedHashMap:

HashMap<Integer, String> attendanceHashMap = new LinkedHashMap<>();
attendanceHashMap.put(1, "John");
attendanceHashMap.put(2, "Jacob");
attendanceHashMap.put(3, "Peter");
attendanceHashMap.put(4, "Clara");
attendanceHashMap.put(5, "Philip");
// printing code follows...

And just for completeness, the Java 8 solution:

attendanceHashMap.forEach((k,v) -> { if(k>=3) System.out.println(k+" "+v); });

Upvotes: 5

Tagir Valeev
Tagir Valeev

Reputation: 100169

Your first problem is that you are using raw Entry type. Replace it with

for(HashMap.Entry<Integer, String> m: ...)

Now m.getKey() will have an Integer type which can be converted to int implicitly without any problems: if(m.getKey()<3).

Another problem is that you are using break instead of continue. Write

if(m.getKey()<3) continue;

The whole fixed loop:

for(HashMap.Entry<Integer, String> m:attendanceHashMap.entrySet()){
    if(m.getKey()<3) continue;
    System.out.println(m.getKey()+" "+m.getValue());
}

Never use rawtypes. It's just a compatibility remnant.

Upvotes: 2

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