Odtnhj

I was wondering is there a collection that I can use for a class Weapon where it's like a hash_set of Weapon objects, but I want to use a name field in my weapon class and make it so that no two Weapons with the same name can exist in the set. I want to compare inputs with strings of my Weapon set to see if it already exists, and if it does, don't put it in the set, but I don't want to search the entire map every single time. Also, it wouldn't be case sensitive.

In your equals(), check only the name field for equality.

public class Weapon 

 private String name;
 // ... other fields

 @Override
 public boolean equals(Object o) getClass() != o.getClass()) return false;

 Weapon weapon = (Weapon) o;

 return name.equalsIgnoreCase(weapon.name); //case-insensitive
 

 @Override
 public int hashCode() 
 return name.toLowerCase().hashCode();
 

And then use your HashSet like so:-

public static void main(String args) 
 Set<Weapon> weapons = new HashSet<>();
 Weapon w1 = new Weapon();
 // TODO set the name of the weapon or pass it in constructor
 if (weapons.add(w1)) 
 System.out.println("Weapon added");
 else 
 System.out.println("Weapon with same name already exists");
 

We have to override equals() and hashcode() methods to return the same interger for name.

Below is the equals() and hashcode () contract:

See JavaDoc of java.lang.Object

In hashCode() it says:

If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.

If you only override equals() and not hashCode() your class violates this contract.

This is also said in the JavaDoc of the equals() method:

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.