给部分方法添加有界通配符。

Author: shengshijun

src/main/java/ssj/algorithm/ArrayUtil.java

@@ -92,15 +92,15 @@ public static <T> void reverse(T[] source, int start, int end) {
         }
     }
 
-    public static <T extends Comparable<T>> void sort(T[] arr) {
+    public static <T extends Comparable<? super T>> void sort(T[] arr) {
         sort(Comparable::compareTo, arr, 0, arr.length - 1);
     }
 
-    public static <T> void sort(T[] arr, Comparator<T> comparator) {
+    public static <T> void sort(T[] arr, Comparator<? super T> comparator) {
         sort(comparator, arr, 0, arr.length - 1);
     }
 
-    private static <T> void sort(Comparator<T> comparator, T[] arr, int start, int end) {
+    private static <T> void sort(Comparator<? super T> comparator, T[] arr, int start, int end) {
         Preconditions.checkNotNull(arr, "arr should not be null");
         Preconditions.checkNotNull(comparator, "comparator should not be null");
         int length = end - start + 1;
@@ -113,11 +113,11 @@ private static <T> void sort(Comparator<T> comparator, T[] arr, int start, int e
     }
 
 
-    private static <T extends Comparable<T>> int partition(T[] arr, int start, int end) {
+    private static <T extends Comparable<? super T>> int partition(T[] arr, int start, int end) {
         return partition(Comparable::compareTo, arr, start, end);
     }
 
-    public static <T> int partition(Comparator<T> comparator, T[] arr, int start, int end) {
+    public static <T> int partition(Comparator<? super T> comparator, T[] arr, int start, int end) {
         int par_index = MathUtil.randInt(start, end);
         ArrayUtil.swap(arr, start, par_index);
         par_index = start;
@@ -140,7 +140,7 @@ public static <T> int partition(Comparator<T> comparator, T[] arr, int start, in
      * @param <T>
      * @return
      */
-    public static <T extends Comparable<T>> T select(T[] arr, int k) {
+    public static <T extends Comparable<? super T>> T select(T[] arr, int k) {
         Preconditions.checkNotNull(arr);
         Preconditions.checkPositionIndex(k, arr.length);
         int low = 0;
@@ -166,7 +166,7 @@ public static <T extends Comparable<T>> T select(T[] arr, int k) {
      * @param <T>
      * @return
      */
-    public <T extends Comparable<T>> int binarySearch(T[] arr, T ele) {
+    public <T extends Comparable<? super T>> int binarySearch(T[] arr, T ele) {
         Preconditions.checkNotNull(arr);
         Preconditions.checkNotNull(ele);
         int low = 0;
@@ -192,13 +192,13 @@ public <T extends Comparable<T>> int binarySearch(T[] arr, T ele) {
      * @param comparator
      * @param <T>
      */
-    public static <T> void mergeSort(T[] arr, Comparator<T> comparator) {
+    public static <T> void mergeSort(T[] arr, Comparator<? super T> comparator) {
         Preconditions.checkNotNull(arr);
         Preconditions.checkNotNull(comparator);
         mergeSort(arr, comparator, 0, arr.length - 1);
     }
 
-    private static <T> void mergeSort(T[] arr, Comparator<T> comparator, int start, int end) {
+    private static <T> void mergeSort(T[] arr, Comparator<? super T> comparator, int start, int end) {
         if (start < end) {
             int middle = (end + start) / 2;
             mergeSort(arr, comparator, start, middle);
@@ -207,10 +207,11 @@ private static <T> void mergeSort(T[] arr, Comparator<T> comparator, int start,
         }
     }
 
-    private static <T> void merge(T[] arr, int start, int middle, int end, Comparator<T> comparator) {
+    private static <T> void merge(T[] arr, int start, int middle, int end, Comparator<? super T> comparator) {
         int front_start = start;
         int end_start = middle + 1;
         int cur_pos = 0;
+        @SuppressWarnings("unchecked")
         T[] helper = (T[]) new Object[end - start + 1];
         while (front_start <= middle && end_start <= end) {
             if (comparator.compare(arr[front_start], arr[end_start]) <= 0) {
@@ -256,7 +257,7 @@ public static void countSort(int[] arr, int start, int end) {
         System.arraycopy(result, 0, arr, 0, arr.length);
     }
 
-    public static <T> void radixSort(T[] arr, Comparator<T> comparator) {
+    public static <T> void radixSort(T[] arr, Comparator<? extends T> comparator) {
         //todo 完成基数排序
     }
 
@@ -310,7 +311,7 @@ public static int[] bitMapSort(int[] un_sort_list) {
      * @param <T>
      * @return
      */
-    public static <T extends Comparable<T>> T minInRotate(T[] arr) {
+    public static <T extends Comparable<? super T>> T minInRotate(T[] arr) {
         Preconditions.checkNotNull(arr);
         if (arr.length == 0) {
             return null;
@@ -336,13 +337,13 @@ public static <T extends Comparable<T>> T minInRotate(T[] arr) {
         return arr[mid];
     }
 
-    public static <T> T[] group(T[] arr, Function<T, Integer> func) {
+    public static <T> T[] group(T[] arr, Function<? super T, ? extends Integer> func) {
         Preconditions.checkNotNull(arr);
         Preconditions.checkNotNull(func);
         TreeMap<Integer, HashSet<T>> static_map = new TreeMap<>();
         for (T ele : arr) {
-            Preconditions.checkNotNull(ele);
-            int group_num = func.apply(ele);
+            Integer group_num = func.apply(ele);
+            Preconditions.checkNotNull(group_num);
             HashSet<T> set = static_map.get(group_num);
             if (set == null) {
                 set = new HashSet<>();
@@ -452,7 +453,7 @@ private static <T> boolean checkMoreThanHalf(T[] arr, T most_ele) {
      * @param <T>
      * @return
      */
-    public static <T extends Comparable<T>> int countEle(T[] arr, T ele) {
+    public static <T extends Comparable<? super T>> int countEle(T[] arr, T ele) {
         Preconditions.checkNotNull(arr);
         Preconditions.checkNotNull(ele);
         int start = getFirstEle(arr, ele);
@@ -468,7 +469,7 @@ public static <T extends Comparable<T>> int countEle(T[] arr, T ele) {
      * @param <T>
      * @return
      */
-    public static <T extends Comparable<T>> int getFirstEle(T[] arr, T ele) {
+    public static <T extends Comparable<? super T>> int getFirstEle(T[] arr, T ele) {
         Preconditions.checkNotNull(arr);
         Preconditions.checkNotNull(ele);
         int start = 0;
@@ -499,7 +500,7 @@ public static <T extends Comparable<T>> int getFirstEle(T[] arr, T ele) {
      * @param <T>
      * @return
      */
-    public static <T extends Comparable<T>> int getLastEle(T[] arr, T ele) {
+    public static <T extends Comparable<? super T>> int getLastEle(T[] arr, T ele) {
         Preconditions.checkNotNull(arr);
         Preconditions.checkNotNull(ele);
         int start = 0;

src/main/java/ssj/algorithm/Collection.java

@@ -14,7 +14,7 @@
 public interface Collection<T> extends Iterable<T>, Cloneable {
     public void add(T ele);
 
-    public default <R> Collection<R> map(Function<T, R> func) {
+    public default <R> Collection<R> map(Function<? super T, ? extends R> func) {
         Preconditions.checkNotNull(func);
         Collection<R> new_collection = newWithCapacity(size());
         for (T ele : this) {
@@ -23,7 +23,7 @@ public default <R> Collection<R> map(Function<T, R> func) {
         return new_collection;
     }
 
-    public default Collection<T> filter(Predicate<T> is_func) {
+    public default Collection<T> filter(Predicate<? super T> is_func) {
         Preconditions.checkNotNull(is_func);
         Collection<T> new_collection = this.newWithZero();
         for (T ele : this) {
@@ -34,7 +34,7 @@ public default Collection<T> filter(Predicate<T> is_func) {
         return new_collection;
     }
 
-    public default <R> R reduce(BiFunction<T, R, R> func, R start) {
+    public default <R> R reduce(BiFunction<? super T, ? super R, ? extends R> func, R start) {
         Preconditions.checkNotNull(func);
         Preconditions.checkNotNull(start);
         R new_start = start;
@@ -85,7 +85,7 @@ public default Vector<T> toVector() {
         return result;
     }
 
-    public default Vector<T> sort(Comparator<T> comparator) {
+    public default Vector<T> sort(Comparator<? super T> comparator) {
         return toVector().sortThis(comparator);
     }
 }

src/main/java/ssj/algorithm/Graph.java

@@ -15,19 +15,19 @@ public interface Graph<T> {
 
     Iterator<T> nodes();
 
-    void dfs(Consumer<T> func);
+    void dfs(Consumer<? super T> func);
 
-    <R> Vector<R> dfs(Function<T, R> func);
+    <R> Vector<R> dfs(Function<? super T, ? extends R> func);
 
-    void bfs(Consumer<T> func);
+    void bfs(Consumer<? super T> func);
 
-    <R> Vector<R> bfs(Function<T, R> func);
+    <R> Vector<R> bfs(Function<? super T, ? extends R> func);
 
     Vector<T> next(T ele);
 
-    void topologicalSort(Consumer<T> func);
+    void topologicalSort(Consumer<? super T> func);
 
-    <R> Vector<R> topologicalSort(Function<T, R> func);
+    <R> Vector<R> topologicalSort(Function<? super T, ? extends R> func);
 
     int size();
 

src/main/java/ssj/algorithm/List.java

@@ -52,7 +52,7 @@ public default T getReverse(int index) {
         return get(normal_index);
     }
 
-    List<T> partition(T par_ele, Comparator<T> comparator);
+    List<T> partition(T par_ele, Comparator<? super T> comparator);
 
     public default Set<T> chainEle() {
         HashSet<T> result = new HashSet<>();

src/main/java/ssj/algorithm/SearchTree.java

@@ -7,7 +7,7 @@
 /**
  * Created by shenshijun on 15/2/5.
  */
-public interface SearchTree<T extends Comparable<T>> extends Iterable<T> {
+public interface SearchTree<T extends Comparable<? super T>> extends Iterable<T> {
     void add(T ele);
 
     default void addAll(Iterable<? extends T> iter) {

src/main/java/ssj/algorithm/Stack.java

@@ -20,7 +20,7 @@ public default boolean isEmpty() {
 
     T head();
 
-    public default Stack<T> sortStack(Comparator<T> comparator) {
+    public default Stack<T> sortStack(Comparator<? super T> comparator) {
         LinkedStack<T> result = new LinkedStack<>();
         while (!isEmpty()) {
             T cur_ele = pop();

src/main/java/ssj/algorithm/collections/AVLTree.java

@@ -12,7 +12,7 @@
 /**
  * Created by shenshijun on 15/2/5.
  */
-public class AVLTree<T extends Comparable<T>> implements SearchTree<T> {
+public class AVLTree<T extends Comparable<? super T>> implements SearchTree<T> {
     private Node _head;
     private int _size;
 

src/main/java/ssj/algorithm/collections/BTree.java

@@ -7,7 +7,7 @@
 /**
  * Created by shenshijun on 15/2/5.
  */
-public class BTree<T extends Comparable<T>> implements SearchTree<T> {
+public class BTree<T extends Comparable<? super T>> implements SearchTree<T> {
     //TODO 完成B树
     @Override
     public void add(T ele) {

src/main/java/ssj/algorithm/collections/ExtensiveStack.java

@@ -3,7 +3,7 @@
 /**
  * Created by shenshijun on 15/2/4.
  */
-public class ExtensiveStack<T extends Comparable<T>> extends LinkedStack<T> {
+public class ExtensiveStack<T extends Comparable<? super T>> extends LinkedStack<T> {
     private LinkedStack<T> _min_stack;
     private LinkedStack<T> _max_stack;
 

src/main/java/ssj/algorithm/collections/LinkedList.java

@@ -103,7 +103,7 @@ public void remove(int index) {
     }
 
     @Override
-    public List<T> partition(T par_ele, Comparator<T> comparator) {
+    public List<T> partition(T par_ele, Comparator<? super T> comparator) {
         Preconditions.checkNotNull(par_ele);
         Preconditions.checkNotNull(comparator);
         Node less_node = _head.getNext();