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Not able initialise ArrayList inside default constructor

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0

I want to declare ArrayList inside my default constructor.
But when I'm doing it, it gives me some problem of reference.

private List<List<Integer>> matrix;

 Matrix(List<List<Integer>> matrix) 
 this.matrix = matrix;
 

 Matrix() 
 this.matrix = new ArrayList<>();
 

I guess it's changing the other instances of that class.

Matrix resultedMatrix = new Matrix();

 List<List<Integer>> resultedMatrix = new ArrayList<>();
 resultedMatrix.add(Arrays.asList(2, 4, 6));
 resultedMatrix.add(Arrays.asList(2, 4, 6));
 resultedMatrix.add(Arrays.asList(2, 4, 6));

 Matrix expected = new Matrix(resultedMatrix);

org.opentest4j.AssertionFailedError:

Expected :com.bootcamp.matrix.Matrix@32cffa6a

Actual :com.bootcamp.matrix.Matrix@792a0fb3

java

share|improve this question

asked Mar 24 at 11:39

Chandan KumarChandan Kumar

15129

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  It's not clear what your problem is.
  
  – Eran
  Mar 24 at 11:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Probably there is other key code involved, code that you're not showing us
  
  – Hovercraft Full Of Eels
  Mar 24 at 11:43
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Please consider reading How to Ask to help us help you
  
  – moneydhaze
  Mar 24 at 11:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Did you expect resultedMatrix == expected to be true? Or perhaps resultedMatrix.equals(expected) to be true? The former cannot be true. The latter can be true if you override equals of your Matrix class.
  
  – Eran
  Mar 24 at 11:47
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Where do you get the org.opentest4j.AssertionFailedError?
  
  – Dorian Gray
  Mar 24 at 11:47
  

  
  
  
  

add a comment | 

0

I want to declare ArrayList inside my default constructor.
But when I'm doing it, it gives me some problem of reference.

private List<List<Integer>> matrix;

 Matrix(List<List<Integer>> matrix) 
 this.matrix = matrix;
 

 Matrix() 
 this.matrix = new ArrayList<>();
 

I guess it's changing the other instances of that class.

Matrix resultedMatrix = new Matrix();

 List<List<Integer>> resultedMatrix = new ArrayList<>();
 resultedMatrix.add(Arrays.asList(2, 4, 6));
 resultedMatrix.add(Arrays.asList(2, 4, 6));
 resultedMatrix.add(Arrays.asList(2, 4, 6));

 Matrix expected = new Matrix(resultedMatrix);

org.opentest4j.AssertionFailedError:

Expected :com.bootcamp.matrix.Matrix@32cffa6a

Actual :com.bootcamp.matrix.Matrix@792a0fb3

java

share|improve this question

asked Mar 24 at 11:39

Chandan KumarChandan Kumar

15129

• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  It's not clear what your problem is.
  
  – Eran
  Mar 24 at 11:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Probably there is other key code involved, code that you're not showing us
  
  – Hovercraft Full Of Eels
  Mar 24 at 11:43
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Please consider reading How to Ask to help us help you
  
  – moneydhaze
  Mar 24 at 11:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Did you expect resultedMatrix == expected to be true? Or perhaps resultedMatrix.equals(expected) to be true? The former cannot be true. The latter can be true if you override equals of your Matrix class.
  
  – Eran
  Mar 24 at 11:47
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Where do you get the org.opentest4j.AssertionFailedError?
  
  – Dorian Gray
  Mar 24 at 11:47
  

  
  
  
  

add a comment | 

I want to declare ArrayList inside my default constructor.
But when I'm doing it, it gives me some problem of reference.

private List<List<Integer>> matrix;

 Matrix(List<List<Integer>> matrix) 
 this.matrix = matrix;
 

 Matrix() 
 this.matrix = new ArrayList<>();
 

I guess it's changing the other instances of that class.

Matrix resultedMatrix = new Matrix();

 List<List<Integer>> resultedMatrix = new ArrayList<>();
 resultedMatrix.add(Arrays.asList(2, 4, 6));
 resultedMatrix.add(Arrays.asList(2, 4, 6));
 resultedMatrix.add(Arrays.asList(2, 4, 6));

 Matrix expected = new Matrix(resultedMatrix);

org.opentest4j.AssertionFailedError:

Expected :com.bootcamp.matrix.Matrix@32cffa6a

Actual :com.bootcamp.matrix.Matrix@792a0fb3

java

share|improve this question

asked Mar 24 at 11:39

Chandan KumarChandan Kumar

15129

private List<List<Integer>> matrix;

 Matrix(List<List<Integer>> matrix) 
 this.matrix = matrix;
 

 Matrix() 
 this.matrix = new ArrayList<>();
 

Matrix resultedMatrix = new Matrix();

 List<List<Integer>> resultedMatrix = new ArrayList<>();
 resultedMatrix.add(Arrays.asList(2, 4, 6));
 resultedMatrix.add(Arrays.asList(2, 4, 6));
 resultedMatrix.add(Arrays.asList(2, 4, 6));

 Matrix expected = new Matrix(resultedMatrix);

share|improve this question

asked Mar 24 at 11:39

Chandan KumarChandan Kumar

15129

share|improve this question

asked Mar 24 at 11:39

Chandan KumarChandan Kumar

15129

asked Mar 24 at 11:39

Chandan KumarChandan Kumar

15129

asked Mar 24 at 11:39

Chandan KumarChandan Kumar

15129

1 Answer
1

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oldest

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0

In Java, the non-primitive variables are saved in the memory and the variables are only reference of the objects in the memory. Which means, that each time you are creating a new object the variable referencing it contains only the memory address in which the object is found.
So when you are creating 2 different objects with the same value they are not equal!!

List<List<Integer>> list1 = new ArrayList<>();
List<List<Integer>> list2 = new ArrayList<>();
list1==list2 //returns false

You can implement an equals function in which it will compare the values of the two objects.

list1.equals(list2)

share|improve this answer

edited Mar 24 at 12:36

answered Mar 24 at 11:57

Nizan IfrachNizan Ifrach

663

add a comment | 

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0

In Java, the non-primitive variables are saved in the memory and the variables are only reference of the objects in the memory. Which means, that each time you are creating a new object the variable referencing it contains only the memory address in which the object is found.
So when you are creating 2 different objects with the same value they are not equal!!

List<List<Integer>> list1 = new ArrayList<>();
List<List<Integer>> list2 = new ArrayList<>();
list1==list2 //returns false

You can implement an equals function in which it will compare the values of the two objects.

list1.equals(list2)

share|improve this answer

edited Mar 24 at 12:36

answered Mar 24 at 11:57

Nizan IfrachNizan Ifrach

663

add a comment | 

0

In Java, the non-primitive variables are saved in the memory and the variables are only reference of the objects in the memory. Which means, that each time you are creating a new object the variable referencing it contains only the memory address in which the object is found.
So when you are creating 2 different objects with the same value they are not equal!!

List<List<Integer>> list1 = new ArrayList<>();
List<List<Integer>> list2 = new ArrayList<>();
list1==list2 //returns false

You can implement an equals function in which it will compare the values of the two objects.

list1.equals(list2)

share|improve this answer

edited Mar 24 at 12:36

answered Mar 24 at 11:57

Nizan IfrachNizan Ifrach

663

add a comment | 

In Java, the non-primitive variables are saved in the memory and the variables are only reference of the objects in the memory. Which means, that each time you are creating a new object the variable referencing it contains only the memory address in which the object is found.
So when you are creating 2 different objects with the same value they are not equal!!

List<List<Integer>> list1 = new ArrayList<>();
List<List<Integer>> list2 = new ArrayList<>();
list1==list2 //returns false

You can implement an equals function in which it will compare the values of the two objects.

list1.equals(list2)

share|improve this answer

edited Mar 24 at 12:36

answered Mar 24 at 11:57

Nizan IfrachNizan Ifrach

663

List<List<Integer>> list1 = new ArrayList<>();
List<List<Integer>> list2 = new ArrayList<>();
list1==list2 //returns false

list1.equals(list2)

share|improve this answer

edited Mar 24 at 12:36

answered Mar 24 at 11:57

Nizan IfrachNizan Ifrach

663

answered Mar 24 at 11:57

Nizan IfrachNizan Ifrach

663

answered Mar 24 at 11:57

Nizan IfrachNizan Ifrach

663