CODEWITHSUNDEEP
java
JasonJL
JasonJL

Reputation: 323

Set value for a class' parameter in Java

I have a java class which has a List as following:

public class TestEntity {
   private String name;
   private List<DataEntry> dataEntries;
}

class DataEntry {
    private String para1;
    private String para2;
    private String para3;
}

How could i add a DataEntry's instance into a TestEntity's instance?

Upvotes: 0

Views: 1740

Answers (3)

GhostCat
GhostCat

Reputation: 140457

First you need to ensure that your list is actually not null, like:

private final List<DataEntry> entries = new ArrayList<>();

and then you can do something like

entries.add(new DataEntry());

or probably more useful:

DataEntry entry = new DataEntry();
entry.para1 = ...

entries.add(entry);

Of course, the more realistic thing would be to add a custom constructor to the DataEntry class, so that you can pass the required arguments via the constructor.

Or, you add a method

void addEntry(DataEntry entry) {
  entries.add(entry);

to your TestEntity class.

Upvotes: 2

Jens
Jens

Reputation: 69440

There are two possiblities:

First: You add a constructor to add an entry:

public class TestEntity {
   private String name;
   private List<DataEntry> dataEntries;
   public TestEntity (String name,DataEntry entry){
     this.name = Name;
     this.dataEntry = new ArrayList<>();
     this.dataEntry.add(entry)
   }
}

Second: You add an addDataEntry function:

public class TestEntity {
   private String name;
   private List<DataEntry> dataEntries;
   public void addDataEntry(DataEntry entry){
     if (this.dataEntry == null){
         this.dataEntry = new ArrayList<>();
     }
     this.dataEntry.add(entry)
   }
}

Upvotes: 1

OcelotcR
OcelotcR

Reputation: 171

Pretty simple if you just instantiate it.

dataEntries.add(new DataEntry());

Upvotes: 1

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