Java Program to implement Bi-Directional Map

This is a Java Program to implement Bi Directional Map. A bi-directional map is an associative data structure in which the (key, value) pairs form a one-to-one correspondence. Thus the binary relation is functional in each direction: value can also act as a key to key. A pair (a, b) thus provides a unique coupling between a and b so that b can be found when a is used as a key and a can be found when b is used as a key.

Here is the source code of the Java Program to implement Bi Directional Map. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

```
/**
```

 ** Java Program to implement Bi Directional Map

```
 **/
```
```
 
```
```
import java.util.Scanner;
```
```
import java.util.HashMap;
```
```
 
```
```
/** class BiDrirectionalMap */
```
```
class BiDirectionalMap
```
```
{
```

    private HashMap<String, String> keyVal;

    private HashMap<String, String> valKey;

```
 
```
```
    /** constructor **/
```
```
    public BiDirectionalMap()
```
```
    {
```

        keyVal = new HashMap<String, String>();

        valKey = new HashMap<String, String>();

```
    }    
```
```
    /** function to clear maps **/
```
```
    public void clear()
```
```
    {
```
```
        keyVal.clear();
```
```
        valKey.clear();
```
```
    }
```

    /** function to get size of maps **/

```
    public int size()
```
```
    {
```
```
        return keyVal.size();
```
```
    }   
```
```
    /** function to insert element **/
```

    public void put(String key, String val)

```
    {
```
```
        keyVal.put(key, val);
```
```
        valKey.put(val, key);
```
```
    }    
```
```
    /** function to get element **/
```
```
    public String get(String ele)
```
```
    {
```
```
        String str = keyVal.get(ele);
```
```
        if (str == null)
```
```
              str = valKey.get(ele);
```
```
 
```
```
        return str;
```
```
    }      
```
```
    /** function to remove element **/
```
```
    public void remove(String key)
```
```
    {
```
```
        String val = keyVal.get(key);
```
```
        if (val != null)
```
```
        {
```
```
            keyVal.remove(key);
```
```
            valKey.remove(val);
```
```
        }
```
```
        else
```
```
        {
```
```
            val = valKey.get(key);
```
```
            if (val != null)
```
```
            {
```
```
                keyVal.remove(val);
```
```
                valKey.remove(key);
```
```
            }
```
```
            else
```

                System.out.println("\nError : Not found\n");

```
        }
```
```
    }        
```
```
}
```
```
 
```
```
/** Class BiDirectionalMapTest **/
```
```
public class BiDirectionalMapTest
```
```
{
```

    public static void main(String[] args)

```
    {
```

        Scanner scan = new Scanner(System.in);

        System.out.println("Bi Directional Map Test\n");

```
 
```

        BiDirectionalMap bdm = new BiDirectionalMap();

```
 
```
```
        char ch;
```

        /** Perform Bi Directional Map operations **/

```
        do    
```
```
        {
```

            System.out.println("\nBi Directional Map <String, String> Operations\n");

            System.out.println("1. put ");

            System.out.println("2. get");

            System.out.println("3. remove");

            System.out.println("4. clear");

            System.out.println("5. size");

```
 
```

            int choice = scan.nextInt();

```
            switch (choice) 
```
```
            {
```
```
            case 1 : 
```

                System.out.println("Enter key and value");

                bdm.put(scan.next(), scan.next() );

                break;

```
            case 2 : 
```

                System.out.println("Enter element");

                String ele = scan.next();

                String str = bdm.get(ele);

```
                if (str != null)
```

                    System.out.println("Result : "+ str);

```
                else
```

                    System.out.println("\nError : Not found\n");

```
                break;        
```
```
            case 3 : 
```

                System.out.println("\nEnter element to be removed");

                bdm.remove(scan.next() );

                break;

```
            case 4 : 
```

                System.out.println("\nBi Directional Map Cleared");

```
                bdm.clear();    
```
```
                break;    
```
```
            case 5 : 
```

                System.out.println("\nSize = "+ bdm.size() );

```
                break;         
```
```
            default : 
```

                System.out.println("Wrong Entry \n ");

```
                break;   
```
```
            }    
```
```
 
```

            System.out.println("\nDo you want to continue (Type y or n) \n");

            ch = scan.next().charAt(0);

        } while (ch == 'Y'|| ch == 'y');

```
    }
```
```
}
```

Bi Directional Map Test
 
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
1
Enter key and value
green mango
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
1
Enter key and value
banana yellow
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
1
Enter key and value
red apple
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
2
Enter element
red
Result : apple
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
2
Enter element
mango
Result : green
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
2
Enter element
apple
Result : red
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
5
 
Size = 3
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
3
 
Enter element to be removed
red
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
2
Enter element
apple
 
Error : Not found
 
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
2
Enter element
red
 
Error : Not found
 
 
Do you want to continue (Type y or n)
 
y
 
Bi Directional Map <String, String> Operations
 
1. put
2. get
3. remove
4. clear
5. size
4
 
Bi Directional Map Cleared
 
Do you want to continue (Type y or n)
 
n

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