Exercise19_10.java

package ch_19;

import java.util.ArrayList;
import java.util.Arrays;

/**
 * 19.10 (Largest element in ArrayList)
 * Write the following method that returns the largest
 * element in an ArrayList:
 * <p>
 * public static <E extends Comparable<E>> E max(ArrayList<E> list)
 */
public class Exercise19_10 {
    public static void main(String[] args) {
        //Test generic method with Double values
        ArrayList<Double> doubleList =
                new ArrayList<>(Arrays.asList(4400.0, 2.2, 6.6, 4400.1, 4.4, 7.7, 1.1, 8.8, 3.3, 5.5, 1203.3, 4400.2,
                        4400.6, 55.2));
        //Test generic method with Integer values
        ArrayList<Integer> integerList =
                new ArrayList<>(Arrays.asList(55, 66, 33, 11, 77, 44, 88, 22));

        System.out.println("The max(ArrayList<E> list) method with a list Doubles returned: " + max(doubleList));
        System.out.println("The max(ArrayList<E> list) method with a list of Integers returned: " + max(integerList));

    }

    public static <E extends Comparable<E>> E max(ArrayList<E> list) {
        if (!list.isEmpty()) {
            E maxValue = list.get(0); // Initialize Max
            for (int i = 1; i < list.size(); i++) {
                E nextValue = list.get(i); // Initialize next value in list
                if (maxValue.compareTo(nextValue) < 0) { // If maxValue is less than nextValue compareTo() returns -1;
                    maxValue = list.get(i); // Set larger value to maxValue
                }
            }
            return maxValue;
        }
        throw new IllegalArgumentException("public static <E extends Comparable<E>> E max(ArrayList<E> list) must be " +
                "passed a NON-empty list.");
    }
}