Making/Initializing Array of Struct Like Objects in Java

Question

I am using Java SE on NetBeans 7.3.1.

I would like to form a Java array similar to the following in C

typedef struct sNewStruct{
    int min;
    int max;
} NewStruct;

NewStruct nsVar[19];

I tried the following

class IntRange{
    int min, max;    
}
IntRange[]  rangeNodes = new IntRange[19];

My problem is that, while rangeNodes is successfully allocated, all of its elements are nulls.

Loop over it and assign new IntRange() to every single one of them. — Kep
– Kep, Commented Sep 1, 2013 at 0:52
why would you think it should contain anything, you never set them to anything? — user177800
– user177800, Commented Sep 1, 2013 at 0:52
You can't really do the stack based allocation that C allows. It's unfortunate coming from C/C++, but that's how Java is. There are answers that show you what you must do. — NG.
– NG., Commented Sep 1, 2013 at 0:54
@JarrodRoberson He would think that because that is how structs work in C/C++, an idea that has no analogue in Java. — Chris Bode
– Chris Bode, Commented Sep 1, 2013 at 1:00

Chris Bode · Accepted Answer · 2013-09-01 00:59:32Z

4

That is how it should behave. Java isn't going to guess that the array should be filled with elements instantiated with the zero-argument constructor. If you want to fill the array, all you need to add is:

for (int i = 0; i < rangeNodes.length; i++)
    rangeNodes[i] = new IntRange();

You could explicitly initialize each element, but this is the cleanest solution.

edited Sep 1, 2013 at 0:59

answered Sep 1, 2013 at 0:53

Chris Bode

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2 Comments

Chris Bode Over a year ago

@JoshM Gotta be faster! :P

Josh M Over a year ago

I was changing songs, will not happen again :)

Josh M · Accepted Answer · 2013-09-01 00:53:50Z

2

As @ccKep is suggesting, you must assign a value to each element in the array:

for(int i = 0; i < rangeNodes.length; i++)
    rangeNodes[i] = new IntRange();

answered Sep 1, 2013 at 0:53

Josh M

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