It s printing out a number every time it finds one that is higher than the current max (which happens to occur three times in your case.) Move the print outside of the for loop and you should be good.

for (int counter = 1; counter < decMax.length; counter++)
{
     if (decMax[counter] > max)
     {
           max = decMax[counter];
     }
}

System.out.println("The highest maximum for the December is: " + max);

To find the highest (max) or lowest (min) value from an array, this could give you the right direction. Here is an example code for getting the highest value from a primitive array.

Method 1:

public int maxValue(int array[]){
  List<Integer> list = new ArrayList<Integer>();
  for (int i = 0; i < array.length; i++) {
    list.add(array[i]);
  }
  return Collections.max(list);
}

To get the lowest value, you can use

Collections.min(list)

Method 2:

public int maxValue(int array[]){
  int max = Arrays.stream(array).max().getAsInt();
  return max;
}

Now the following line should work.

System.out.println("The highest maximum for the December is: " + maxValue(decMax)); 

You need to print out the max after you ve scanned all of them:

for (int counter = 1; counter < decMax.length; counter++)
{
    if (decMax[counter] > max)
    {
        max = decMax[counter];
        // not here: System.out.println("The highest maximum for the December is: " + max);
    }
}  
System.out.println("The highest maximum for the December is: " + max);

If you are looking for the quickest and simplest way to perform various actions in regards to arrays, the use of the Collections class is extremely helpful (documentation available from https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html), actions ranges from finding the maximum, minimum, sorting, reverse order, etc.

A simple way to find the maximum value from the array with the use of Collections:

Double[] decMax = {-2.8, -8.8, 2.3, 7.9, 4.1, -1.4, 11.3, 10.4, 8.9, 8.1, 5.8, 5.9, 7.8, 4.9, 5.7, -0.9, -0.4, 7.3, 8.3, 6.5, 9.2, 3.5, 3.0, 1.1, 6.5, 5.1, -1.2, -5.1, 2.0, 5.2, 2.1};
List<Double> a = new ArrayList<Double>(Arrays.asList(decMax));
System.out.println("The highest maximum for the December is: " + Collections.max(a));

If you are interested in finding the minimum value, similar to finding maximum:

System.out.println(Collections.min(a));

The simplest line to sort the list:

Collections.sort(a);

Or alternatively the use of the Arrays class to sort an array:

Arrays.sort(decMax);

However the Arrays class does not have a method that refers to the maximum value directly, sorting it and referring to the last index is the maximum value, however keep in mind sorting by the above 2 methods has a complexity of O(n log n).

Same as suggested by others, just mentioning the cleaner way of doing it:

int max = decMax[0];
for(int i=1;i<decMax.length;i++)
    max = Math.max(decMax[i],max);
System.out.println("The Maximum value is : " + max);

A shorter solution to have the max value of array:

double max = Arrays.stream(decMax).max(Double::compareTo).get();

You have your print() statement in the for() loop, It should be after so that it only prints once. the way it currently is, every time the max changes it prints a max.

If you don t want to use any java predefined libraries then below is the

simplest way

   public class Test {

    public static void main(String[] args) {
        double[] decMax = {-2.8, -8.8, 2.3, 7.9, 4.1, -1.4, 11.3, 10.4,
            8.9, 8.1, 5.8, 5.9, 7.8, 4.9, 5.7, -0.9, -0.4, 7.3, 8.3, 6.5, 9.2,
            3.5, 3, 1.1, 6.5, 5.1, -1.2, -5.1, 2, 5.2, 2.1};

        double maxx = decMax[0];

        for (int i = 0; i < decMax.length; i++) {
            if (maxx < decMax[i]) {
                maxx = decMax[i];
            }
        }
        System.out.println(maxx);

    }
}

You can use a function that accepts a array and finds the max value in it. i made it generic so it could also accept other data types

public static <T extends Comparable<T>> T findMax(T[] array){       
    T max = array[0];
    for(T data: array){
        if(data.compareTo(max)>0)
            max =data;                
    }
    return max;
}

You can write like this.

import java.util.Scanner;
class   BigNoArray{

    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter how many array element");
        int n=sc.nextInt();
        int[] ar= new int[n];
        System.out.println("enter "+n+" values");
        for(int i=0;i<ar.length;i++){
            ar[i]=sc.nextInt();
        }
        int fbig=ar[0];
        int sbig=ar[1];
        int tbig=ar[3];
            for(int i=1;i<ar.length;i++){
                if(fbig<ar[i]){
                    sbig=fbig;
                    fbig=ar[i];
                }
                else if(sbig<ar[i]&&ar[i]!=fbig){
                    sbig=ar[i];
                }
                else if(tbig<ar[i]&&ar[i]!=fbig){
                    tbig=ar[i];
                }
            }
        System.out.println("first big number is "+fbig);
        System.out.println("second big number is "+sbig);
        System.out.println("third big number is "+tbig);
    }
}

void FindMax()
{
    int lessonNum;

    System.out.print("Enter your lesson numbers : ");
    lessonNum = input.nextInt();
    int[] numbers = new int[lessonNum];
    for (int i = 0; i < numbers.length; i++)
    {
        System.out.print("Please enter " + (i + 1) + " number : ");
        numbers[i] = input.nextInt();
    }
    double max = numbers[0];
    for (int i = 1; i < numbers.length; i++)
    {
        if (numbers[i] > max)
        {
            max = numbers[i];
        }
    }
    System.out.println("Maximum number is : " + max);
}

You are just Compare zeroth element with rest of the elements so it will print the value last largest value which it will contain, in you case, same problem is happening. To compare each and every elements we have to swap the values like:

double max = decMax[0];
    for (int counter = 1; counter < decMax.length; counter++){
        if(max<decMax[i]){
            max=decMax[i]; //swapping
            decMax[i]=decMax[0];
        }
    }
    System.out.println("The max value is "+ max);

Hope this will help you

Easiest way which I ve found, supports all android versions

Arrays.sort(series1Numbers);

int maxSeries = Integer.parseInt(String.valueOf(series1Numbers[series1Numbers.length-1]));

An easy way without using collections

public void findHighestNoInArray() {
        int[] a = {1,2,6,8,9};
        int large = a[0];
            for(int num : a) {
                if(large < num) {
                    large = num;
                }
            }
            System.out.println("Large number is "+large+"");
        }

import java.util.*;
class main9 //Find the smallest and 2lagest and  ascending and descending order of  elements in array//
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter the array range");
        int no=sc.nextInt();
        System.out.println("Enter the array element");
        int a[]=new int[no];
        int i;
        for(i=0;i<no;i++)
        {
            a[i]=sc.nextInt();
        }
        Arrays.sort(a);
        int s=a[0];
        int l=a[a.length-1];
        int m=a[a.length-2];
        System.out.println("Smallest no is="+s);
        System.out.println("lagest 2 numbers are=");
        System.out.println(l);
        System.out.println(m);
        System.out.println("Array in ascending:");
        for(i=0;i<no;i++)
        {
            System.out.println(a[i]);
        }
        System.out.println("Array in descending:");
        for(i=a.length-1;i>=0;i--)
        {
            System.out.println(a[i]);
        }
    }
}

simple way find max number

   int arr[] = {10, 11, 12, 13, 55, 18, 20};
    int num = arr.length;
    int max = 0;

    for (int i = 0; i < num; i++) {
        if (arr[i] > max) {
            max = arr[i];

        }

    }
    System.out.println(max);

    package Loops;
    import java.util.Scanner;
    public class LargestNumber {
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            System.out.println("How many numbers you want to enter?
");
            int x = sc.nextInt();
            int[] data = new int[x];
            for (int i = 0; i < data.length; i++) {
                System.out.println("Enter the number " + (i + 1));
                data[i] = sc.nextInt();
            }
            int max = data[0];
            int min = data[0];
            int i;
            for (i = 1; i < data.length; i++) {
                if (data[i] > max) {
                    max = data[i];
                } else if (data[i] < min) {
                    min = data[i];
                }
            }
            System.out.println("The highest number in array is: " + max);
            System.out.println("The smallest number in array is: " + min);
        }
    }

    int[] data2 = {1,10,50,70};
    List<Integer> testing= new ArrayList<>();
    for(int s=0;s<data.length;s++){
        testing.add(data[s]);
                }
    int t= Collections.max(testing);
    int mini= Collections.min(testing);
    System.out.println("Max is:"+t);
    System.out.println("Minimum  is:"+mini);

function maxElement(values){
  var max = values[0]; // Initialize maximum element
  for (value of values){ //Traverse array elements from second and compare every element with curr`enter code here`ent max 
    if (value > max) {
      max = value //new maximum
    }
  }
  return max;
}