What is Java Guava | Lists.partition() method with Examples?

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Java Guava | Lists.partition() method with Examples️‍🔥

The Lists.partition() method in Guava Library is used to divide the original list into sublists of the same size. The method accepts two parameters.

For example: If the original list passed as parameter is [a, b, c, d, e] and the partition size is 3, then the sublists yield are as [[a, b, c], [d, e]].

Syntax:

public static <T> List<List<T>> partition(List<T> list, int size)

Parameters: The method accepts two parameters:

list: The list which is to be divided into sublists based on the partition size.
size: The desired size of each sublist. The size of the last sublist may be smaller.

Return Value: The method returns the list of consecutive sublists. Each sublist(except possibly the last one) has the size equal to the partition size.

Exception: The method Lists.partition() throws IllegalArgumentException if partition size is non-positive.

Below examples illustrate the implementation of above method:

Example 1:

// Java code to show implementation of 
// Guava's Lists.partition() method 
  
import com.google.common.collect.Lists; 
import java.util.Arrays; 
import java.util.List; 
  
class GFG { 
  
    // Driver's code 
    public static void main(String[] args) 
    { 
        // Creating a List of Integers 
        List<Integer> myList 
            = Arrays.asList(1, 2, 3, 4, 5); 
  
        // Using Lists.partition() method to divide 
        // the original list into sublists of the same 
        // size, which are just views of the original list. 
        // The final list may be smaller. 
        List<List<Integer> > lists 
            = Lists.partition(myList, 2); 
  
        // Displaying the sublists 
        for (List<Integer> sublist: lists) 
            System.out.println(sublist); 
    } 
} 

Output:

[1, 2]
[3, 4]
[5]

Example 2:

// Java code to show implementation of 
// Guava's Lists.partition() method 
  
import com.google.common.collect.Lists; 
import java.util.Arrays; 
import java.util.List; 
  
class GFG { 
  
    // Driver's code 
    public static void main(String[] args) 
    { 
  
        // Creating a List of Characters 
        List<Character> myList 
            = Arrays.asList('H', 'E', 'L', 'L', 'O', 
                            'G', 'E', 'E', 'K', 'S'); 
  
        // Using Lists.partition() method to divide 
        // the original list into sublists of the same 
        // size, which are just views of the original list. 
        // The final list may be smaller. 
        List<List<Character> > lists 
            = Lists.partition(myList, 3); 
  
        // Displaying the sublists 
        for (List<Character> sublist: lists) 
            System.out.println(sublist); 
    } 
} 

Output:

[H, E, L]
[L, O, G]
[E, E, K]
[S]

Reference: https://google.github.io/guava/releases/23.0/api/docs/com/google/common/collect/Lists.html#partition-java.util.List-int-