Initial data commit

Task/Stream-merge/Java/stream-merge.java

@@ -0,0 +1,100 @@
+import java.util.Iterator;
+import java.util.List;
+import java.util.Objects;
+
+public class StreamMerge {
+    private static <T extends Comparable<T>> void merge2(Iterator<T> i1, Iterator<T> i2) {
+        T a = null, b = null;
+
+        while (i1.hasNext() || i2.hasNext()) {
+            if (null == a && i1.hasNext()) {
+                a = i1.next();
+            }
+            if (null == b && i2.hasNext()) {
+                b = i2.next();
+            }
+
+            if (null != a) {
+                if (null != b) {
+                    if (a.compareTo(b) < 0) {
+                        System.out.print(a);
+                        a = null;
+                    } else {
+                        System.out.print(b);
+                        b = null;
+                    }
+                } else {
+                    System.out.print(a);
+                    a = null;
+                }
+            } else if (null != b) {
+                System.out.print(b);
+                b = null;
+            }
+        }
+
+        if (null != a) {
+            System.out.print(a);
+        }
+        if (null != b) {
+            System.out.print(b);
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    @SafeVarargs
+    private static <T extends Comparable<T>> void mergeN(Iterator<T>... iter) {
+        Objects.requireNonNull(iter);
+        if (iter.length == 0) {
+            throw new IllegalArgumentException("Must have at least one iterator");
+        }
+
+        Object[] pa = new Object[iter.length];
+        boolean done;
+
+        do {
+            done = true;
+
+            for (int i = 0; i < iter.length; i++) {
+                Iterator<T> t = iter[i];
+                if (null == pa[i] && t.hasNext()) {
+                    pa[i] = t.next();
+                }
+            }
+
+            T min = null;
+            int idx = -1;
+            for (int i = 0; i < pa.length; ++i) {
+                T t = (T) pa[i];
+                if (null != t) {
+                    if (null == min) {
+                        min = t;
+                        idx = i;
+                        done = false;
+                    } else if (t.compareTo(min) < 0) {
+                        min = t;
+                        idx = i;
+                        done = false;
+                    }
+                }
+            }
+            if (idx != -1) {
+                System.out.print(min);
+                pa[idx] = null;
+            }
+        } while (!done);
+    }
+
+    public static void main(String[] args) {
+        List<Integer> l1 = List.of(1, 4, 7, 10);
+        List<Integer> l2 = List.of(2, 5, 8, 11);
+        List<Integer> l3 = List.of(3, 6, 9, 12);
+
+        merge2(l1.iterator(), l2.iterator());
+        System.out.println();
+
+        mergeN(l1.iterator(), l2.iterator(), l3.iterator());
+        System.out.println();
+        System.out.flush();
+    }
+}