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Java How to remove item from nested Array List

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1

I have a nested ArrayList as below with boolean values. I want to remove for example 3rd item from all the rows. I tried with a loop but it doesnt resolve remove as a method. How should I do this? Many thanks for your help.

for (int i = 0; i < list.size(); i++)
 list.get(i).remove(3)// this remove method shows as an error in IDE
 

true false true false false false
false false true false true true

java list nested nested-lists

share|improve this question

edited Mar 24 at 9:44

YCF_L

34.8k104687

asked Mar 24 at 8:37

user4046073user4046073

3371417

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  what's the type of list? perhaps you are using raw types.
  
  – Eran
  Mar 24 at 8:40
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  your list look like List<List<Boolean>> list
  
  – YCF_L
  Mar 24 at 8:40
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Eran It's a list of List<Instance> listInstances = new ArrayList<Instance>(); and the class Instance has vals = new ArrayList<Boolean>(); Let me know if it explains a bit
  
  – user4046073
  Mar 24 at 8:44
  
  

  
  
  
  

add a comment | 

1

I have a nested ArrayList as below with boolean values. I want to remove for example 3rd item from all the rows. I tried with a loop but it doesnt resolve remove as a method. How should I do this? Many thanks for your help.

for (int i = 0; i < list.size(); i++)
 list.get(i).remove(3)// this remove method shows as an error in IDE
 

true false true false false false
false false true false true true

java list nested nested-lists

share|improve this question

edited Mar 24 at 9:44

YCF_L

34.8k104687

asked Mar 24 at 8:37

user4046073user4046073

3371417

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  what's the type of list? perhaps you are using raw types.
  
  – Eran
  Mar 24 at 8:40
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  your list look like List<List<Boolean>> list
  
  – YCF_L
  Mar 24 at 8:40
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Eran It's a list of List<Instance> listInstances = new ArrayList<Instance>(); and the class Instance has vals = new ArrayList<Boolean>(); Let me know if it explains a bit
  
  – user4046073
  Mar 24 at 8:44
  
  

  
  
  
  

add a comment | 

I have a nested ArrayList as below with boolean values. I want to remove for example 3rd item from all the rows. I tried with a loop but it doesnt resolve remove as a method. How should I do this? Many thanks for your help.

for (int i = 0; i < list.size(); i++)
 list.get(i).remove(3)// this remove method shows as an error in IDE
 

true false true false false false
false false true false true true

java list nested nested-lists

share|improve this question

edited Mar 24 at 9:44

YCF_L

34.8k104687

asked Mar 24 at 8:37

user4046073user4046073

3371417

for (int i = 0; i < list.size(); i++)
 list.get(i).remove(3)// this remove method shows as an error in IDE
 

true false true false false false
false false true false true true

share|improve this question

edited Mar 24 at 9:44

YCF_L

34.8k104687

asked Mar 24 at 8:37

user4046073user4046073

3371417

share|improve this question

edited Mar 24 at 9:44

YCF_L

34.8k104687

asked Mar 24 at 8:37

user4046073user4046073

3371417

edited Mar 24 at 9:44

YCF_L

34.8k104687

edited Mar 24 at 9:44

YCF_L

34.8k104687

asked Mar 24 at 8:37

user4046073user4046073

3371417

asked Mar 24 at 8:37

user4046073user4046073

3371417

3 Answers
3

active

oldest

votes

2

... It's a list of List<Instance> listInstances = new
ArrayList<Instance>(); and the class Instance has vals = new
ArrayList<Boolean>(); ....

In this case your solution can look like :

public static Instance deleleNthElement(Instance instance, int index) 
 instance.getVals().remove(index - 1);
 return instance;

then with stream you can call the method like so :

int index = 3;
listInstances = listInstances.stream()
 .map(instance -> deleleNthElement(instance, index))
 .collect(Collectors.toList());

share|improve this answer

edited Mar 24 at 9:32

answered Mar 24 at 8:43

YCF_LYCF_L

34.8k104687

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I only want to remove the 3rd item. Would this keep the first 3?
  
  – user4046073
  Mar 24 at 8:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @user4046073 I thought you want to delete the first three element, check my edit I think you need that solution instead the first
  
  – YCF_L
  Mar 24 at 8:52
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. Which package do I need to import? I added import java.util.List; but that did not work.. it does not resolve subList and Collectors. I imported import java.util.*; too I am running Java java 11.0.2
  
  – user4046073
  Mar 24 at 9:00
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user4046073 yes there are, I was wrong, I think all you need is remove, check my answer and gives me a feedback please
  
  – YCF_L
  Mar 24 at 9:26
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user4046073 please edit your question and put the Instance class and more code please to understand more, in your case you have List<Instance> listInstances and each instance have List<Boolean> vals, so to remove a val from each vals of each instanace you have to get the vals and remove the element from it, again show me more code so I can help you
  
  – YCF_L
  Mar 24 at 9:41
  

  
  
  
  

 | 
show 6 more comments

2

I see no error in your logic, I believe you are missing a ';' from the end of the remove(3).

By the way, List is an Interface, you will need to instanciate as an ArrayList (or some such).

share|improve this answer

answered Mar 24 at 9:24

Bill NaylorBill Naylor

7117

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. Yes sorry I have that ; in my code. But somehow that remove does not get resolved. I could remove a whole row but not the n th item in that row
  
  – user4046073
  Mar 24 at 9:28
  

  
  
  
  

add a comment | 

1

I strung the following together, seems to do what you intended:

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test 

 public static void main(String[] args) throws IOException 

 List<Boolean> row1 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,false,true,true));
 List<Boolean> row2 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,true,false,true));
 List<List<Boolean>> list = Arrays.asList(new ArrayList[] (ArrayList) row1, (ArrayList) row2);

 for (int i=0;i<list.size();i++)
 list.get(i).remove(3);// this remove method shows as an error in IDE
 
 for (List<Boolean> ll : list) 
 for (Boolean l : ll) 
 System.out.print(l + ",");
 
 System.out.println();
 
 

share|improve this answer

answered Mar 24 at 10:07

Bill NaylorBill Naylor

7117

add a comment | 

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2

... It's a list of List<Instance> listInstances = new
ArrayList<Instance>(); and the class Instance has vals = new
ArrayList<Boolean>(); ....

In this case your solution can look like :

public static Instance deleleNthElement(Instance instance, int index) 
 instance.getVals().remove(index - 1);
 return instance;

then with stream you can call the method like so :

int index = 3;
listInstances = listInstances.stream()
 .map(instance -> deleleNthElement(instance, index))
 .collect(Collectors.toList());

share|improve this answer

edited Mar 24 at 9:32

answered Mar 24 at 8:43

YCF_LYCF_L

34.8k104687

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I only want to remove the 3rd item. Would this keep the first 3?
  
  – user4046073
  Mar 24 at 8:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @user4046073 I thought you want to delete the first three element, check my edit I think you need that solution instead the first
  
  – YCF_L
  Mar 24 at 8:52
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. Which package do I need to import? I added import java.util.List; but that did not work.. it does not resolve subList and Collectors. I imported import java.util.*; too I am running Java java 11.0.2
  
  – user4046073
  Mar 24 at 9:00
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user4046073 yes there are, I was wrong, I think all you need is remove, check my answer and gives me a feedback please
  
  – YCF_L
  Mar 24 at 9:26
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user4046073 please edit your question and put the Instance class and more code please to understand more, in your case you have List<Instance> listInstances and each instance have List<Boolean> vals, so to remove a val from each vals of each instanace you have to get the vals and remove the element from it, again show me more code so I can help you
  
  – YCF_L
  Mar 24 at 9:41
  

  
  
  
  

 | 
show 6 more comments

2

... It's a list of List<Instance> listInstances = new
ArrayList<Instance>(); and the class Instance has vals = new
ArrayList<Boolean>(); ....

In this case your solution can look like :

public static Instance deleleNthElement(Instance instance, int index) 
 instance.getVals().remove(index - 1);
 return instance;

then with stream you can call the method like so :

int index = 3;
listInstances = listInstances.stream()
 .map(instance -> deleleNthElement(instance, index))
 .collect(Collectors.toList());

share|improve this answer

edited Mar 24 at 9:32

answered Mar 24 at 8:43

YCF_LYCF_L

34.8k104687

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I only want to remove the 3rd item. Would this keep the first 3?
  
  – user4046073
  Mar 24 at 8:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @user4046073 I thought you want to delete the first three element, check my edit I think you need that solution instead the first
  
  – YCF_L
  Mar 24 at 8:52
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. Which package do I need to import? I added import java.util.List; but that did not work.. it does not resolve subList and Collectors. I imported import java.util.*; too I am running Java java 11.0.2
  
  – user4046073
  Mar 24 at 9:00
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user4046073 yes there are, I was wrong, I think all you need is remove, check my answer and gives me a feedback please
  
  – YCF_L
  Mar 24 at 9:26
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @user4046073 please edit your question and put the Instance class and more code please to understand more, in your case you have List<Instance> listInstances and each instance have List<Boolean> vals, so to remove a val from each vals of each instanace you have to get the vals and remove the element from it, again show me more code so I can help you
  
  – YCF_L
  Mar 24 at 9:41
  

  
  
  
  

 | 
show 6 more comments

... It's a list of List<Instance> listInstances = new
ArrayList<Instance>(); and the class Instance has vals = new
ArrayList<Boolean>(); ....

In this case your solution can look like :

public static Instance deleleNthElement(Instance instance, int index) 
 instance.getVals().remove(index - 1);
 return instance;

then with stream you can call the method like so :

int index = 3;
listInstances = listInstances.stream()
 .map(instance -> deleleNthElement(instance, index))
 .collect(Collectors.toList());

share|improve this answer

edited Mar 24 at 9:32

answered Mar 24 at 8:43

YCF_LYCF_L

34.8k104687

public static Instance deleleNthElement(Instance instance, int index) 
 instance.getVals().remove(index - 1);
 return instance;

int index = 3;
listInstances = listInstances.stream()
 .map(instance -> deleleNthElement(instance, index))
 .collect(Collectors.toList());

share|improve this answer

edited Mar 24 at 9:32

answered Mar 24 at 8:43

YCF_LYCF_L

34.8k104687

answered Mar 24 at 8:43

YCF_LYCF_L

34.8k104687

answered Mar 24 at 8:43

YCF_LYCF_L

34.8k104687

2

I see no error in your logic, I believe you are missing a ';' from the end of the remove(3).

By the way, List is an Interface, you will need to instanciate as an ArrayList (or some such).

share|improve this answer

answered Mar 24 at 9:24

Bill NaylorBill Naylor

7117

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. Yes sorry I have that ; in my code. But somehow that remove does not get resolved. I could remove a whole row but not the n th item in that row
  
  – user4046073
  Mar 24 at 9:28
  

  
  
  
  

add a comment | 

2

I see no error in your logic, I believe you are missing a ';' from the end of the remove(3).

By the way, List is an Interface, you will need to instanciate as an ArrayList (or some such).

share|improve this answer

answered Mar 24 at 9:24

Bill NaylorBill Naylor

7117

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. Yes sorry I have that ; in my code. But somehow that remove does not get resolved. I could remove a whole row but not the n th item in that row
  
  – user4046073
  Mar 24 at 9:28
  

  
  
  
  

add a comment | 

I see no error in your logic, I believe you are missing a ';' from the end of the remove(3).

By the way, List is an Interface, you will need to instanciate as an ArrayList (or some such).

share|improve this answer

answered Mar 24 at 9:24

Bill NaylorBill Naylor

7117

share|improve this answer

answered Mar 24 at 9:24

Bill NaylorBill Naylor

7117

answered Mar 24 at 9:24

Bill NaylorBill Naylor

7117

answered Mar 24 at 9:24

Bill NaylorBill Naylor

7117

1

I strung the following together, seems to do what you intended:

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test 

 public static void main(String[] args) throws IOException 

 List<Boolean> row1 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,false,true,true));
 List<Boolean> row2 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,true,false,true));
 List<List<Boolean>> list = Arrays.asList(new ArrayList[] (ArrayList) row1, (ArrayList) row2);

 for (int i=0;i<list.size();i++)
 list.get(i).remove(3);// this remove method shows as an error in IDE
 
 for (List<Boolean> ll : list) 
 for (Boolean l : ll) 
 System.out.print(l + ",");
 
 System.out.println();
 
 

share|improve this answer

answered Mar 24 at 10:07

Bill NaylorBill Naylor

7117

add a comment | 

1

I strung the following together, seems to do what you intended:

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test 

 public static void main(String[] args) throws IOException 

 List<Boolean> row1 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,false,true,true));
 List<Boolean> row2 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,true,false,true));
 List<List<Boolean>> list = Arrays.asList(new ArrayList[] (ArrayList) row1, (ArrayList) row2);

 for (int i=0;i<list.size();i++)
 list.get(i).remove(3);// this remove method shows as an error in IDE
 
 for (List<Boolean> ll : list) 
 for (Boolean l : ll) 
 System.out.print(l + ",");
 
 System.out.println();
 
 

share|improve this answer

answered Mar 24 at 10:07

Bill NaylorBill Naylor

7117

add a comment | 

I strung the following together, seems to do what you intended:

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test 

 public static void main(String[] args) throws IOException 

 List<Boolean> row1 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,false,true,true));
 List<Boolean> row2 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,true,false,true));
 List<List<Boolean>> list = Arrays.asList(new ArrayList[] (ArrayList) row1, (ArrayList) row2);

 for (int i=0;i<list.size();i++)
 list.get(i).remove(3);// this remove method shows as an error in IDE
 
 for (List<Boolean> ll : list) 
 for (Boolean l : ll) 
 System.out.print(l + ",");
 
 System.out.println();
 
 

share|improve this answer

answered Mar 24 at 10:07

Bill NaylorBill Naylor

7117

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Test 

 public static void main(String[] args) throws IOException 

 List<Boolean> row1 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,false,true,true));
 List<Boolean> row2 = new ArrayList<Boolean>(Arrays.asList(new Boolean[] true,true,false,true));
 List<List<Boolean>> list = Arrays.asList(new ArrayList[] (ArrayList) row1, (ArrayList) row2);

 for (int i=0;i<list.size();i++)
 list.get(i).remove(3);// this remove method shows as an error in IDE
 
 for (List<Boolean> ll : list) 
 for (Boolean l : ll) 
 System.out.print(l + ",");
 
 System.out.println();
 
 

share|improve this answer

answered Mar 24 at 10:07

Bill NaylorBill Naylor

7117

answered Mar 24 at 10:07

Bill NaylorBill Naylor

7117

answered Mar 24 at 10:07

Bill NaylorBill Naylor

7117