﻿ Java - Length of the longest consecutive sequence of an array

# Java: Find the length of the longest consecutive sequence of a given array of integers

## Java Basic: Exercise-170 with Solution

Write a Java program to find the length of the longest consecutive sequence in a given array of integers.

Visual Presentation: Sample Solution:

Java Code:

``````// Importing the required Java utilities package
import java.util.*;

// Defining a class named Solution
public class Solution {

// Method to find the length of the longest sequence in an array
public static int longest_sequence(int[] nums) {
// Checking if the input array is null
if (nums == null) {
throw new IllegalArgumentException("Null array..!"); // Throwing an exception for a null array
}

// Checking if the array is empty
if (nums.length == 0) {
return 0; // Returning 0 if the array is empty
}

boolean flag = false; // Initializing a flag to track the presence of a sequence
int result = 0; // Initializing the variable to store the length of the longest sequence
int start = 0, end = 0; // Initializing variables to track the start and end of a sequence

// Loop to iterate through the array elements
for (int i = 1; i < nums.length; i++) {
// Checking if the current element is greater than the previous element
if (nums[i - 1] < nums[i]) {
end = i; // Updating the end of the sequence if the condition is met
} else {
start = i; // Updating the start of the sequence if the condition is not met
}

// Checking if the length of the current sequence is greater than the stored result
if (end - start > result) {
flag = true; // Setting the flag to indicate the presence of a longer sequence
result = end - start; // Updating the result with the length of the longer sequence
}
}

// Returning the length of the longest sequence
if (flag) {
return result + 1; // Adding 1 to the result if a sequence is found
} else {
return result; // Returning the result if no sequence is found
}
}

// The main method of the program
public static void main(String[] args) {
int[] nums = { 1, 1, 2, 3, 3, 4, 5, 2, 4, 5, 6, 7, 8, 9, 6, -1, -2 }; // Initializing an array

// Displaying the original array
System.out.println("\nOriginal array: " + Arrays.toString(nums));

// Finding and displaying the length of the longest sequence in the array
System.out.println(longest_sequence(nums));
}
}
```
```

Sample Output:

```Original array: [1, 1, 2, 3, 3, 4, 5, 2, 4, 5, 6, 7, 8, 9, 6, -1, -2]
7
```

Flowchart: Java Code Editor: