Check values of HashMap <Object,String>

Question

I have an IntPair class which has two methods I use from it: "getFirst()" and "getSecond()". While in this method I'm currently working, I want to check if "hashMap j" contains a specific value and then do the actions. I think I have the problem in these lines:

Object obj = j.values();
t.moveCursor(((IntPair)obj).getFirst(), ((IntPair)obj).getSecond());

I don't know if I'm casting ok to the Object, or if the first line "Object obj = j.values()" should be replaced with another method call. I tested with a System.out.print ("Message") after j.containsValue("0") and I got the message back.

This is a part of the method I'm trying to make it work.

public static HashMap<IntPair, String> j = new HashMap<>();

j.put(new IntPair(firstInt, secondInt), value);
if (j.containsValue("0"))
{
Object obj = j.values();
t.moveCursor(((IntPair)obj).getFirst(), ((IntPair)obj).getSecond());
t.putCharacter('x');
}
else if (j.containsValue("1"))
{
Object obj = j.values();
t.moveCursor(((IntPair)obj).getFirst(), ((IntPair)obj).getSecond());
t.putCharacter('v');
}

IntPair Class:

public class IntPair {
private final int first;
private final int second;

public IntPair(int first, int second) {
    this.first = first;
    this.second = second;
}

@Override
public int hashCode() {
    int hash = 3;
    hash = 89 * hash + this.first;
    hash = 89 * hash + this.second;
    return hash;
}

@Override
public boolean equals(Object obj) {
    if (obj == null) {
        return false;
    }
    if (getClass() != obj.getClass()) {
        return false;
    }
    final IntPair other = (IntPair) obj;
    if (this.first != other.first) {
        return false;
    }
    if (this.second != other.second) {
        return false;
    }
    return true;
}

public int getFirst() {
    return first;
}

public int getSecond() {
    return second;
}
}

Any help would be really appreciated. Thank you!

1) I don't see a complete method where you state, "this is the method...". 2) I assume (and certainly hope) that your IntPair class overrides equals and hashCode() appropriately, correct? 3) I am not sure what exactly it is you're asking or that you're stuck on. You mention a question about casting -- is your attempt to cast causing an error or exception? — Hovercraft Full Of Eels
– Hovercraft Full Of Eels, Commented Jan 17, 2015 at 2:12

monika arora · Accepted Answer · 2015-05-28 06:21:19Z

There is a big issue with the code you have written In line

t.moveCursor(((IntPair)obj).getFirst(), ((IntPair)obj).getSecond());

the expression

((IntPair)obj).getFirst()

wont return the getFirst value as obj here is not of type IntPair but obj is a collection of elements IntPair returned by

Object obj = j.values();

so you have to retrieve IntPair element from this collection and then you can read getFirst() I have written a small program to make my point

public static HashMap<IntPair, String> j = new HashMap<IntPair, String>();

    public static void main(String[] args) {
        j.put(new IntPair(2, 3), "0");
        if (j.containsValue("0")) {
            Set<Entry<IntPair, String>> pairs = j.entrySet();
            Iterator<Entry<IntPair, String>> it = pairs.iterator();
            Entry e;
            while (it.hasNext()) {
                e = it.next();
                if (e.getValue().equals("0")) {
                    IntPair resultObj = (IntPair) e.getKey();
                }
            }

        }
    }

Hovercraft Full Of Eels · Accepted Answer · 2015-01-17 02:16:04Z

0

Note that the values() method returns a Collection of the values objects, here a Collection of Strings. You can't cast this to IntPair, and I'm surprised that your attempt is not causing a compiler error.

answered Jan 17, 2015 at 2:16

Hovercraft Full Of Eels

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3 Comments

Xhens Over a year ago

I edited the question. What should I use instead of values() ?

Hovercraft Full Of Eels Over a year ago

@XhensB: what are you trying to achieve? What error(s) are you seeing?

Xhens Over a year ago

I'm not getting any error but the code is not working for me. I have a terminal screen and I want to take values from hashMap and than pass them as arguments at the method moveCursor(int x, int y). After I move the cursor to desired location, I want to fill it with characters. And the result is that I have a blank screen in the end.

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