CODEWITHSUNDEEP
javaclasshashmaphashset
Supersonic
Supersonic

Reputation: 11

How to modify variable class from HashSet or HashMap of Class

I have a HashSet and a HashMap of Class. How to modify the class variable? so I have a class Data, then I create HashSet of Data and HashMap of Data then do population. later, I would like to modify the value name and number. 

class Data {
private String name;
private int number;

public Data(String name, int number) {
    this.name = name;
    this.number = number;
}

public String toString() {
    return name + ":" + number;
}
public void modifyNumber (int i) {
    this.number+=i;
} }

public class Main {

public static void main(String[] args) {
Set<Data> dataSet = new LinkedHashSet<Data>();
 Map<String, Data> map = new LinkedHashMap<String, Data>();
 // I do the dataSet and map population, then do something else
 //now I want to modify the value of name and number  for HashSet and HashMap of Class
}}

Upvotes: 0

Views: 288

Answers (2)

Siva Kumar
Siva Kumar

Reputation: 2006

To work inside a HashSet, the Data class should override equals and hashcode methods.

Otherwise the set will not operate as expected.

In your implementation you failed to override those methods.

But when you do that, you cannot change the attribute values which are used in equals and hashcode. This may cause the object to be in the wrong hash bucket for its new value.

You can change the other attributes.

hashset.iterator.next().setXXX();

Upvotes: 1

Bruce
Bruce

Reputation: 8849

create the getter and setter method for Data class then get the object and change it

public void setName(String name){
this.name=name;
}

map.get("id").setName("newname");
map.get("id").modifyNumber(number);

Upvotes: 1

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