Find Second Largest in array

import java.lang.*;
import java.util.*;

public class Main {

    public static void findLargestAndSecondLargestVal(int[] a){
        int aLen = a.length;
	
        if(validateError(a)){
            System.out.print("NA");
        }
        else{
            int greaterVal = a[0];

            for(int j=0; j<aLen; j++){
                if(greaterVal < a[j]){
                    greaterVal = a[j];
                }
            }
            //System.out.println("Largest val: "+greaterVal);
            getsecond(a, greaterVal);
        }
    }

    public static boolean validateError(int[] ar){
        int arLen = ar.length;
		//System.out.println("Len: "+arLen);
        if(arLen <= 0){
            return true;
        }
        int count = 1;
        for(int i=0; i<arLen-1; i++){
			//System.out.println("check: "+ar[i]+ " - "+ ar[i+1]);
            if(ar[i] == ar[i+1]){
                count++; 
            }
        }
       // System.out.println("count==arLen: "+count+" "+arLen);
        if(count == arLen){
            return true;
        }
        return false;
    }

    public static void getsecond(int[] a2, int b){
        int a2Len = a2.length;
        int secondLargest = a2[0];

        for(int k=1; k<a2Len; k++){
            if(a2[k] != b &&  secondLargest < a2[k]){
                secondLargest = a2[k];
            }
        }
        System.out.println(secondLargest);
    }

    public static void main(String[] args) {
        // YOUR CODE GOES HERE
        // Please take input and print output to standard input/output (stdin/stdout)
        // DO NOT USE ARGUMENTS FOR INPUTS
        // E.g. 'Scanner' for input & 'System.out' for output
        Scanner sc = new Scanner(System.in);
        int arrLen = sc.nextInt();
        int[] arr = new int[arrLen];

        for(int i=0; i<arrLen; i++){
            arr[i] = sc.nextInt();
        }

        findLargestAndSecondLargestVal(arr);
        
    }
}