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Projekte/common/src/main/java/pp/util/Util.java

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+////////////////////////////////////////
+// Programming project code
+// UniBw M, 2022, 2023, 2024
+// www.unibw.de/inf2
+// (c) Mark Minas (mark.minas@unibw.de)
+////////////////////////////////////////
+
+package pp.util;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * A class with auxiliary functions.
+ */
+public class Util {
+    private Util() { /* do not instantiate */ }
+
+    /**
+     * Calculates and returns the area of a polygon defined by a list of points, using the shoelace formula.
+     * The result is positive if the sequence of vertices is in clockwise order, and negative
+     * otherwise.
+     *
+     * @param points A list of positions that define the vertices of the polygon in planar coordinates.
+     * @return The calculated area of the polygon.
+     */
+    public static float getArea(List<? extends Position> points) {
+        float sum = 0;
+        Position prev = getLast(points);
+        for (var next : points) {
+            sum += prev.getX() * next.getY() - next.getX() * prev.getY();
+            prev = next;
+        }
+        return 0.5f * sum;
+    }
+
+    /**
+     * Returns the last element of the given list.
+     *
+     * @param list the list from which to retrieve the last element
+     * @param <T>  the type of elements in the list
+     * @return the last element of the list
+     * @throws IndexOutOfBoundsException if the list is empty
+     */
+    public static <T> T getLast(List<T> list) {
+        return list.get(list.size() - 1);
+    }
+
+    /**
+     * Reverses the order of elements in the given list.
+     *
+     * @param list the list to be reversed
+     * @param <T>  the type of elements in the list
+     * @return a new list with elements in reversed order
+     */
+    public static <T> List<T> reverse(List<T> list) {
+        final List<T> reversed = new ArrayList<>(list);
+        Collections.reverse(reversed);
+        return reversed;
+    }
+
+    /**
+     * Creates a copy of the given list.
+     *
+     * @param list the list to be copied, may be null
+     * @param <T>  the type of elements in the list
+     * @return a new list containing the elements of the original list, or null if the original list is null
+     */
+    public static <T> List<T> copy(List<T> list) {
+        return list == null ? null : new ArrayList<>(list);
+    }
+
+    /**
+     * Adds an element to a set and returns a new set containing the original elements and the new element.
+     *
+     * @param set     the original set, must not be null
+     * @param element the element to be added to the set
+     * @param <T>     the type of elements in the set
+     * @param <E>     the type of the element being added, must extend T
+     * @return a new set containing the original elements and the new element
+     */
+    public static <T, E extends T> Set<T> add(Set<T> set, E element) {
+        final Set<T> newSet = new HashSet<>(set);
+        newSet.add(element);
+        return newSet;
+    }
+}