Question

How to convert an iterator to a list in Java

Answer 1

import java.util.List;
import java.util.Arrays;
import java.util.Iterator;
import java.util.ArrayList;
    
public class MyClass {
    public static <T> List<T>
    getListFromIterator(Iterator<T> it) {
        List<T> list = new ArrayList<>();
   
        it.forEachRemaining(list::add);
   
        return list;
    }
     
    public static void main(String args[]) {
        Iterator<Integer> it = Arrays.asList(1, 2, 3, 4, 5, 6, 7).iterator();
   
        List<Integer> list = getListFromIterator(it);
   
        System.out.println(list);
    }
}
    
    
    
    
    
/*
run:
    
[1, 2, 3, 4, 5, 6, 7]
  
*/

 

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Answer 2

import java.util.List;
import java.util.Arrays;
import java.util.Iterator;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
   
public class MyClass {
    public static <T> List<T>
    getListFromIterator(Iterator<T> it) {
        Iterable<T> iterable = ()->it;
  
        List<T> list = StreamSupport
                            .stream(iterable.spliterator(), false)
                            .collect(Collectors.toList());
  
        return list;
    }
    
    public static void main(String args[]) {
        Iterator<String> it = Arrays.asList("java", "c", "c++", "python").iterator();
  
        List<String> list = getListFromIterator(it);
  
        System.out.println(list);
    }
}
   
   
   
   
   
/*
run:
   
[java, c, c++, python]
 
*/

 

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Answer 3

import java.util.List;
import java.util.Arrays;
import java.util.Iterator;
import java.util.ArrayList;
 
public class MyClass {
    public static void main(String args[]) {
        Iterator<Integer> iterator = Arrays.asList(1, 2, 3, 4, 5, 6, 7).iterator();
  
        List<Integer> list = new ArrayList<>();
         
        iterator.forEachRemaining(list::add);    
         
        System.out.println(list);
    }
}
 
 
 
 
/*
run:
 
[1, 2, 3, 4, 5, 6, 7]
 
*/

 

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