Dynamically creating a 2D array in Groovy

I have already gone through all the questions on stackoverflow regarding Groovy 2D arrays and the answers do not seem to suffice. I am also fairly new to groovy hence, I'd sincerely appreciate your input in this regard.

I am trying to create a 2D array in the following way.

def extractedArray = 
// fullArray is a 2D array of size[11987][4]

def x = 0
for (x; x<fullArray.length; x++)
 if (x==0)

 extractedArray = 

 extractedArray[0][0]=fullArray[0][0]
 extractedArray[0][1]=fullArray[0][2]
 
 else

 for(def y=0; y<extractedArray.length; y++)
 //other functions

But this seems to give me the following error.

Caught: java.lang.NullPointerException: Cannot invoke method putAt() on null object
java.lang.NullPointerException: Cannot invoke method putAt() on null object
 at computeMPR.main(computeMPR.groovy:37)

edited Nov 16 '18 at 6:54

Kartik

4,45731537

asked Nov 16 '18 at 6:51

Nayantara Jeyaraj

1,77541742

add a comment |

I am trying to create a 2D array in the following way.

def extractedArray = 
// fullArray is a 2D array of size[11987][4]

def x = 0
for (x; x<fullArray.length; x++)
 if (x==0)

 extractedArray = 

 extractedArray[0][0]=fullArray[0][0]
 extractedArray[0][1]=fullArray[0][2]
 
 else

 for(def y=0; y<extractedArray.length; y++)
 //other functions

But this seems to give me the following error.

Caught: java.lang.NullPointerException: Cannot invoke method putAt() on null object
java.lang.NullPointerException: Cannot invoke method putAt() on null object
 at computeMPR.main(computeMPR.groovy:37)

edited Nov 16 '18 at 6:54

Kartik

4,45731537

asked Nov 16 '18 at 6:51

Nayantara Jeyaraj

1,77541742

add a comment |

I am trying to create a 2D array in the following way.

def extractedArray = 
// fullArray is a 2D array of size[11987][4]

def x = 0
for (x; x<fullArray.length; x++)
 if (x==0)

 extractedArray = 

 extractedArray[0][0]=fullArray[0][0]
 extractedArray[0][1]=fullArray[0][2]
 
 else

 for(def y=0; y<extractedArray.length; y++)
 //other functions

But this seems to give me the following error.

Caught: java.lang.NullPointerException: Cannot invoke method putAt() on null object
java.lang.NullPointerException: Cannot invoke method putAt() on null object
 at computeMPR.main(computeMPR.groovy:37)

edited Nov 16 '18 at 6:54

Kartik

4,45731537

asked Nov 16 '18 at 6:51

Nayantara Jeyaraj

1,77541742

I am trying to create a 2D array in the following way.

def extractedArray = 
// fullArray is a 2D array of size[11987][4]

def x = 0
for (x; x<fullArray.length; x++)
 if (x==0)

 extractedArray = 

 extractedArray[0][0]=fullArray[0][0]
 extractedArray[0][1]=fullArray[0][2]
 
 else

 for(def y=0; y<extractedArray.length; y++)
 //other functions

But this seems to give me the following error.

Caught: java.lang.NullPointerException: Cannot invoke method putAt() on null object
java.lang.NullPointerException: Cannot invoke method putAt() on null object
 at computeMPR.main(computeMPR.groovy:37)

arrays dynamic groovy 2d

edited Nov 16 '18 at 6:54

Kartik

4,45731537

asked Nov 16 '18 at 6:51

Nayantara Jeyaraj

1,77541742

edited Nov 16 '18 at 6:54

Kartik

4,45731537

asked Nov 16 '18 at 6:51

Nayantara Jeyaraj

1,77541742

edited Nov 16 '18 at 6:54

Kartik

4,45731537

edited Nov 16 '18 at 6:54

Kartik

4,45731537

edited Nov 16 '18 at 6:54

Kartik

4,45731537

asked Nov 16 '18 at 6:51

Nayantara Jeyaraj

1,77541742

asked Nov 16 '18 at 6:51

Nayantara Jeyaraj

1,77541742

asked Nov 16 '18 at 6:51

Nayantara Jeyaraj

1,77541742

add a comment |

1 Answer
1

active

oldest

votes

def extractedArray =

this is not array but List initialization

so you can change code:

//extractedArray[0][0]=fullArray[0][0]
//extractedArray[0][1]=fullArray[0][2]
extractedArray << [fullArray[0][0], fullArray[0][2]]

or if you prefer arrays you can do something like:

Object extractedArray = [fullArray.size()]

extractedArray[0] = [
 fullArray[0][0],
 fullArray[0][2]
 ] as Object

answered Nov 16 '18 at 7:38

Evgeny Smirnov

2,0811618

Thanks for your response. But this is the problem. With Object extractedArray = [fullArray.size()], we're creating the extractedArray with the same size as the fullArray right? But, in my case, we don't know the size of the extractedArray. I simply want to define the array without specifying a size. Then as we push the values to the array, it dynamically increases in size.

– Nayantara Jeyaraj
Nov 16 '18 at 10:24

Since we initially don't know how many elements we'll be storing in the array, the array needs to dynamically grow as the elements are inserted. I know how to do this with the other scripting languages like JS, but not exactly sure about groovy. Any suggestions? Thanks.

– Nayantara Jeyaraj
Nov 16 '18 at 10:26

You can't change the size of an array once created. You either have to allocate it bigger than you think you'll need or accept the overhead of having to reallocate it needs to grow in size.

– Evgeny Smirnov
Nov 16 '18 at 10:53

But this is possible with Javascript right? We simple declare an array and then as we array.push('x') elements to it, the array size increases as well. Isn't the same possible with groovy?

– Nayantara Jeyaraj
Nov 19 '18 at 3:40

Groovy is based on Java. In java there are no way to create array with dynamic size. Collections are developed to solve this problem. List is much more powerful structure then regular array. And if you need array on the end you can simply transform list to array: list.toArray(new Object[list.size()])

– Evgeny Smirnov
Nov 19 '18 at 6:42

|
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1 Answer
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active

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1 Answer
1

active

oldest

votes

def extractedArray =

this is not array but List initialization

so you can change code:

//extractedArray[0][0]=fullArray[0][0]
//extractedArray[0][1]=fullArray[0][2]
extractedArray << [fullArray[0][0], fullArray[0][2]]

or if you prefer arrays you can do something like:

Object extractedArray = [fullArray.size()]

extractedArray[0] = [
 fullArray[0][0],
 fullArray[0][2]
 ] as Object

answered Nov 16 '18 at 7:38

Evgeny Smirnov

2,0811618

Thanks for your response. But this is the problem. With Object extractedArray = [fullArray.size()], we're creating the extractedArray with the same size as the fullArray right? But, in my case, we don't know the size of the extractedArray. I simply want to define the array without specifying a size. Then as we push the values to the array, it dynamically increases in size.

– Nayantara Jeyaraj
Nov 16 '18 at 10:24

Since we initially don't know how many elements we'll be storing in the array, the array needs to dynamically grow as the elements are inserted. I know how to do this with the other scripting languages like JS, but not exactly sure about groovy. Any suggestions? Thanks.

– Nayantara Jeyaraj
Nov 16 '18 at 10:26

You can't change the size of an array once created. You either have to allocate it bigger than you think you'll need or accept the overhead of having to reallocate it needs to grow in size.

– Evgeny Smirnov
Nov 16 '18 at 10:53

But this is possible with Javascript right? We simple declare an array and then as we array.push('x') elements to it, the array size increases as well. Isn't the same possible with groovy?

– Nayantara Jeyaraj
Nov 19 '18 at 3:40

Groovy is based on Java. In java there are no way to create array with dynamic size. Collections are developed to solve this problem. List is much more powerful structure then regular array. And if you need array on the end you can simply transform list to array: list.toArray(new Object[list.size()])

– Evgeny Smirnov
Nov 19 '18 at 6:42

|
show 1 more comment

def extractedArray =

this is not array but List initialization

so you can change code:

//extractedArray[0][0]=fullArray[0][0]
//extractedArray[0][1]=fullArray[0][2]
extractedArray << [fullArray[0][0], fullArray[0][2]]

or if you prefer arrays you can do something like:

Object extractedArray = [fullArray.size()]

extractedArray[0] = [
 fullArray[0][0],
 fullArray[0][2]
 ] as Object

answered Nov 16 '18 at 7:38

Evgeny Smirnov

2,0811618

Thanks for your response. But this is the problem. With Object extractedArray = [fullArray.size()], we're creating the extractedArray with the same size as the fullArray right? But, in my case, we don't know the size of the extractedArray. I simply want to define the array without specifying a size. Then as we push the values to the array, it dynamically increases in size.

– Nayantara Jeyaraj
Nov 16 '18 at 10:24

Since we initially don't know how many elements we'll be storing in the array, the array needs to dynamically grow as the elements are inserted. I know how to do this with the other scripting languages like JS, but not exactly sure about groovy. Any suggestions? Thanks.

– Nayantara Jeyaraj
Nov 16 '18 at 10:26

You can't change the size of an array once created. You either have to allocate it bigger than you think you'll need or accept the overhead of having to reallocate it needs to grow in size.

– Evgeny Smirnov
Nov 16 '18 at 10:53

But this is possible with Javascript right? We simple declare an array and then as we array.push('x') elements to it, the array size increases as well. Isn't the same possible with groovy?

– Nayantara Jeyaraj
Nov 19 '18 at 3:40

Groovy is based on Java. In java there are no way to create array with dynamic size. Collections are developed to solve this problem. List is much more powerful structure then regular array. And if you need array on the end you can simply transform list to array: list.toArray(new Object[list.size()])

– Evgeny Smirnov
Nov 19 '18 at 6:42

|
show 1 more comment

def extractedArray =

this is not array but List initialization

so you can change code:

//extractedArray[0][0]=fullArray[0][0]
//extractedArray[0][1]=fullArray[0][2]
extractedArray << [fullArray[0][0], fullArray[0][2]]

or if you prefer arrays you can do something like:

Object extractedArray = [fullArray.size()]

extractedArray[0] = [
 fullArray[0][0],
 fullArray[0][2]
 ] as Object

answered Nov 16 '18 at 7:38

Evgeny Smirnov

2,0811618

def extractedArray =

this is not array but List initialization

so you can change code:

//extractedArray[0][0]=fullArray[0][0]
//extractedArray[0][1]=fullArray[0][2]
extractedArray << [fullArray[0][0], fullArray[0][2]]

or if you prefer arrays you can do something like:

Object extractedArray = [fullArray.size()]

extractedArray[0] = [
 fullArray[0][0],
 fullArray[0][2]
 ] as Object

answered Nov 16 '18 at 7:38

Evgeny Smirnov

2,0811618

answered Nov 16 '18 at 7:38

Evgeny Smirnov

2,0811618

answered Nov 16 '18 at 7:38

Evgeny Smirnov

2,0811618

answered Nov 16 '18 at 7:38

Evgeny Smirnov

2,0811618

Thanks for your response. But this is the problem. With Object extractedArray = [fullArray.size()], we're creating the extractedArray with the same size as the fullArray right? But, in my case, we don't know the size of the extractedArray. I simply want to define the array without specifying a size. Then as we push the values to the array, it dynamically increases in size.

– Nayantara Jeyaraj
Nov 16 '18 at 10:24

Since we initially don't know how many elements we'll be storing in the array, the array needs to dynamically grow as the elements are inserted. I know how to do this with the other scripting languages like JS, but not exactly sure about groovy. Any suggestions? Thanks.

– Nayantara Jeyaraj
Nov 16 '18 at 10:26

You can't change the size of an array once created. You either have to allocate it bigger than you think you'll need or accept the overhead of having to reallocate it needs to grow in size.

– Evgeny Smirnov
Nov 16 '18 at 10:53

But this is possible with Javascript right? We simple declare an array and then as we array.push('x') elements to it, the array size increases as well. Isn't the same possible with groovy?

– Nayantara Jeyaraj
Nov 19 '18 at 3:40

Groovy is based on Java. In java there are no way to create array with dynamic size. Collections are developed to solve this problem. List is much more powerful structure then regular array. And if you need array on the end you can simply transform list to array: list.toArray(new Object[list.size()])

– Evgeny Smirnov
Nov 19 '18 at 6:42

|
show 1 more comment

Thanks for your response. But this is the problem. With Object extractedArray = [fullArray.size()], we're creating the extractedArray with the same size as the fullArray right? But, in my case, we don't know the size of the extractedArray. I simply want to define the array without specifying a size. Then as we push the values to the array, it dynamically increases in size.

– Nayantara Jeyaraj
Nov 16 '18 at 10:24

Since we initially don't know how many elements we'll be storing in the array, the array needs to dynamically grow as the elements are inserted. I know how to do this with the other scripting languages like JS, but not exactly sure about groovy. Any suggestions? Thanks.

– Nayantara Jeyaraj
Nov 16 '18 at 10:26

You can't change the size of an array once created. You either have to allocate it bigger than you think you'll need or accept the overhead of having to reallocate it needs to grow in size.

– Evgeny Smirnov
Nov 16 '18 at 10:53

But this is possible with Javascript right? We simple declare an array and then as we array.push('x') elements to it, the array size increases as well. Isn't the same possible with groovy?

– Nayantara Jeyaraj
Nov 19 '18 at 3:40

Groovy is based on Java. In java there are no way to create array with dynamic size. Collections are developed to solve this problem. List is much more powerful structure then regular array. And if you need array on the end you can simply transform list to array: list.toArray(new Object[list.size()])

– Evgeny Smirnov
Nov 19 '18 at 6:42

Thanks for your response. But this is the problem. With Object extractedArray = [fullArray.size()], we're creating the extractedArray with the same size as the fullArray right? But, in my case, we don't know the size of the extractedArray. I simply want to define the array without specifying a size. Then as we push the values to the array, it dynamically increases in size.

– Nayantara Jeyaraj
Nov 16 '18 at 10:24

Since we initially don't know how many elements we'll be storing in the array, the array needs to dynamically grow as the elements are inserted. I know how to do this with the other scripting languages like JS, but not exactly sure about groovy. Any suggestions? Thanks.

– Nayantara Jeyaraj
Nov 16 '18 at 10:26

You can't change the size of an array once created. You either have to allocate it bigger than you think you'll need or accept the overhead of having to reallocate it needs to grow in size.

– Evgeny Smirnov
Nov 16 '18 at 10:53

But this is possible with Javascript right? We simple declare an array and then as we array.push('x') elements to it, the array size increases as well. Isn't the same possible with groovy?

– Nayantara Jeyaraj
Nov 19 '18 at 3:40

Groovy is based on Java. In java there are no way to create array with dynamic size. Collections are developed to solve this problem. List is much more powerful structure then regular array. And if you need array on the end you can simply transform list to array: list.toArray(new Object[list.size()])

– Evgeny Smirnov
Nov 19 '18 at 6:42

|
show 1 more comment

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