print max num in an array in java

Question

import java.util.Scanner;

public class maxnuminarray {
    public static void main(String[] args) {
        int temp;
        System.out.print("please insert the size for array:");
        Scanner input = new Scanner(System.in);
        int size = input.nextInt();
        int[] nums = new int[size];

        for (int i = 0; i < size; i++) {
            System.out.print("please insert your desired nums:");
            nums[i] = input.nextInt();
        }

        for (int i = 1; i < size; i++)
            for (int j = 0; j < size - i; j++)
                if (nums[i] > nums[i + 1]) {
                    temp = nums[i];
                    nums[i] = nums[i + 1];
                    nums[i + 1] = temp;
                }

        System.out.print(nums[size - 1]);
    }
}

Though it gets all the values for the array, it still doesn't print the max number which is the last num in the array.

The error I get for size=5:

Exception in thread "main": java.lang.ArrayIndexOutOfBoundsException: Index 5 out of bounds for length 5 at maxnuminarray.main(maxnuminarray.java:15)

Answer 1

Once you read in the values, iterate over the array like this.

int max = Integer.MIN_VALUE;
for (int n : nums) {
   max = Math.max(max, n);
}

Answer 2

You're trying to get a value with an index that doesn't exist. For instance, at if (nums[i] > nums[i + 1]). Let's say you have 3 numbers in total, your array size will be 3, but your index starts at 0.

Index 0	Index 1	Index 2
5	10	21

If you try to get i + 1 when i = 2 you get an error since i = 3 does not exist.

Also, if you're trying to get the largest number out of the array, you only need to go through the array once.

int[] nums = new int[]{1, 10, 3};
int max = nums[0];

for (int i = 1; i < nums.length; i++)
    if (max < nums[i])
        max = nums[i];

Or you can use Collections with the Integer[] array.

int max = Collections.max(Arrays.asList(num));

Answer 3

If you are just looking to find the maximum in the array, @Nouredine's code should do the trick.

Your code is comparing consecutive numbers one by one through the array, and swapping them in a bubble sort kind of way.

But if you are really looking to move the maximum in the array to the last position in the array, you can use this piece of code. The issue in your code is you are accessing 5th index in an array of size 5, where only 0,1,2,3,4 are allowed.

    for (int i = 1; i < size; i++)
        if (nums[i - 1] > nums[i]) {
            temp = nums[i - 1];
            nums[i - 1] = nums[i];
            nums[i] = temp;
        }
    }   

Answer 4

import java.util.Scanner;
public class maxnuminarray {
public static void main(String[] args) {
    int temp;
    System.out.print("please insert the size for array:");
    Scanner input = new Scanner(System.in);
    int size = input.nextInt();
    int[] nums = new int[size];
    for (int i = 0; i < size; i++) {
        System.out.print("please insert your desired nums:");
        nums[i] = input.nextInt();
    }
    int max = nums[0];
    for (int i = 1; i < size; i++)
       if(max < nums[i])
          max = nums[i];
   }
   System.out.println("Max " + max);
}