Makes a new utility class containing methods related to lists

src/main/java/net/knarcraft/ffmpegconverter/utility/ListUtil.java

@@ -0,0 +1,81 @@
+package net.knarcraft.ffmpegconverter.utility;
+
+import java.lang.reflect.Array;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Predicate;
+
+/**
+ * A class which helps with operations on lists
+ */
+public final class ListUtil {
+
+    private ListUtil() {
+    }
+
+    /**
+     * Combines two arrays to one
+     * @param listA <p>The first array.</p>
+     * @param listB <p>The second array.</p>
+     * @param <T> <p>The type of the two lists.</p>
+     * @return <p>A new array containing all elements from the two arrays.</p>
+     */
+    static <T> T[] concatenate(T[] listA, T[] listB) {
+        int listALength = listA.length;
+        int listBLength = listB.length;
+        @SuppressWarnings("unchecked")
+        T[] resultList = (T[]) Array.newInstance(listA.getClass().getComponentType(), listALength + listBLength);
+        System.arraycopy(listA, 0, resultList, 0, listALength);
+        System.arraycopy(listB, 0, resultList, listALength, listBLength);
+        return resultList;
+    }
+
+    /**
+     * Gets all list items according to the predicate
+     * @param list <p>The list to process.</p>
+     * @param predicate <p>The predicate to test.</p>
+     * @param <T> <p>The type of the list.</p>
+     * @return <p>A new list containing all matching elements.</p>
+     */
+    static <T> List<T> getMatching(List<T> list, Predicate<T> predicate) {
+        List<T> copy = new ArrayList<>(list);
+        list.removeIf(predicate);
+        copy.removeAll(list);
+        return copy;
+    }
+
+    /**
+     * Tests if any element in a list fulfills a condition.
+     *
+     * @param list      The list to test against
+     * @param predicate A predicate to use on every element in the list
+     * @param <T>       Anything which can be stored in a list
+     * @return          True if at least one element fulfills the predicate
+     */
+    static <T> boolean listContains(T[] list, Predicate<T> predicate) {
+        for (T item : list) {
+            if (predicate.test(item)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Gets a list from a comma separated string at index in list
+     * @param list <p>A list of tokens.</p>
+     * @param index <p>The index of the token containing comma separated entries.</p>
+     * @return <p>A string list.</p>
+     */
+    public static String[] getList(List<String> list, int index) {
+        String[] result = null;
+        if (list.size() > index) {
+            if (list.get(index).contains(",")) {
+                result = list.get(index).split(",");
+            } else {
+                result = new String[]{list.get(index)};
+            }
+        }
+        return result;
+    }
+}