Initialize array of custom class

Question

I'd like to initialize an array of objects (contrived example)

class StringPair {
    String a;
    String b;
    // constructor
}

StringPair p[] = {
    { "a", "b" },
    { "c", "d" }
};

But javac complains java: illegal initializer for StringPair for definition of p

How should I write this?

score 6 · Answer 1 · answered Apr 24 '17 at 06:30

6

You should invoke the constructor :

StringPair[] p = { new StringPair ("a", "b"), new StringPair ("c", "d") };

answered Apr 24 '17 at 06:30

Eran

374,785
51
663
734

score 2 · Accepted Answer · edited May 23 '17 at 12:34

2

Use new Operator inside {}. difference between object and variable

StringPair p[] = {
    new StringPair("a", "b"),
    new StringPair("c", "d")
};

edited May 23 '17 at 12:34

Community

1
1

answered Apr 24 '17 at 06:31

sovas

1,418
10
23

Pau · Answer 3 · 2017-04-24T07:25:25.213

1

If you are not able to create a constructor with params, you could use double brace initialization:

StringPair p[] = {
    new StringPair(){{
      setA("a");
      setB("b");
    }},
     new StringPair(){{
      setA("c");
      setB("d");
    }}
};

It seems like something you are looking for.

edited Apr 24 '17 at 07:25

answered Apr 24 '17 at 07:20

Pau

13,250
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88

score 0 · Answer 4 · answered Apr 24 '17 at 06:31

following list initialization (name taken from C++) is not a valid java way to init an array:

StringPair p[] = {
    { "a", "b" },
    { "c", "d" }
};

do instead use the constructor of your class:

StringPair p[] = { new StringPair("a", "b"), new StringPair("1", "g") };

score 0 · Answer 5 · answered Apr 24 '17 at 06:31

0

You need to pass object's of StringPair

like below code

StringPair p[] = { new StringPair ("a", "b"), new StringPair ("c", "d") };

answered Apr 24 '17 at 06:31

Chetan Joshi

5,442
4
27
38

score 0 · Answer 6 · answered Apr 24 '17 at 06:38

0

You should Create a constructor like this

class StringPair {
String a;
String b;

Public StringPair(string a, string b)
{
this.a=a;
this.b=b;
}
}

then you can initialize it like this

StringPair p[] = { new StringPair("a", "b"), new StringPair("c", "d") };

answered Apr 24 '17 at 06:38

Ashok Rayal

375
2
15

mark it as answer if it solves your problem, thanks :) – Ashok Rayal Apr 24 '17 at 06:39
2

how is this different from other answers? do not post duplicate answers – Courage Apr 24 '17 at 06:58

score 0 · Answer 7 · answered Jul 13 '18 at 19:35

I don't know why so many people keep posting the same solution.

In my case, I needed to initialize an array of objects. However, these objects were generated from XSD, so I'm not able to add a custom constructor. We'd need C# with partial classes for that.

Pau above gave me the hint to solve it, but his solution doesn't compile. Here's one that does:

StringPair p[] = new StringPair[] {
    new StringPair(){{
      setA("a");
      setB("b");
    }},
     new StringPair(){{
      setA("c");
      setB("d");
    }}
};

Initialize array of custom class

7 Answers7