 # Java Exercises: Create maximum number of regions obtained by drawing n given straight lines

## Java Basic: Exercise-234 with Solution

If you draw a straight line on a plane, the plane is divided into two regions. For example, if you pull two straight lines in parallel, you get three areas, and if you draw vertically one to the other you get 4 areas.

Write a Java program to create maximum number of regions obtained by drawing n given straight lines.
Input:
(1 ≤ n ≤ 10,000)

Sample Solution:

Java Code:

``````import java.util.*;

public class Main {
public static void main(String[] args){
Scanner scan = new Scanner(System.in);
System.out.println("Input number of straight lines:");
int n=scan.nextInt();
System.out.println("Number of regions:");
System.out.println((n * (n + 1) >> 1) + 1);
}
}
```
```

Sample Output:

```Input number of straight lines:
5
Number of regions:
16
```

Pictorial Presentation: Flowchart: Java Code Editor:

What is the difficulty level of this exercise?

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## Java: Tips of the Day

Array vs ArrayLists:

The main difference between these two is that an Array is of fixed size so once you have created an Array you cannot change it but the ArrayList is not of fixed size. You can create instances of ArrayLists without specifying its size. So if you create such instances of an ArrayList without specifying its size Java will create an instance of an ArrayList of default size.

Once an ArrayList is full it re-sizes itself. In fact, an ArrayList is internally supported by an array. So when an ArrayList is resized it will slow down its performance a bit as the contents of the old Array must be copied to a new Array.

At the same time, it's compulsory to specify the size of an Array directly or indirectly while creating it. And also Arrays can store both primitives and objects while ArrayLists only can store objects.

Ref: https://bit.ly/3o8L2KH