Merge pull request #2 from bloder/take-drop

Add Take and Drop function

seq/src/main/java/com/jmonad/seq/Seq.java

@@ -270,6 +270,34 @@ public <Ret> Seq<T> uniqueBy(Function<Ret, T> fn) {
     return buffer;
   }
 
+  /**
+   * Returns the first n elements of the sequence
+   * @param amount
+   * @return Seq<T>
+   */
+  public Seq<T> take(int amount) {
+    Seq<T> buffer = new Seq<>();
+    if (amount <= 0) return buffer;
+    if (amount > this.list.size()) return new Seq<>(this.list);
+
+    for (int i = 0; i < amount; i++) buffer.add(this.list.get(i));
+    return buffer;
+  }
+
+  /**
+   * Remove the first n elements of the sequence
+   * @param amount
+   * @return Seq<T>
+   */
+  public Seq<T> drop(int amount) {
+    Seq<T> buffer = new Seq<>();
+    if (amount <= 0) return new Seq<>(this.list);
+    if (amount > this.list.size()) return buffer;
+
+    for (int i = amount; i < this.list.size(); i++) buffer.add(this.list.get(i));
+    return buffer;
+  }
+
   /**
    * Takes a list of items, and using the binary function supplied, folds them
    * into a single value. Requires an initial value (the second argument),

seq/src/test/java/com/jmonad/seq/SeqDropTest.java

@@ -0,0 +1,25 @@
+package com.jmonad.seq;
+
+import org.junit.Test;
+
+public class SeqDropTest {
+
+  private Integer[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  private Seq<Integer> elements = new Seq<>(numbers);
+
+  @Test public void dropListElementsTest() {
+    assert elements.drop(5).toArrayList().toString().equals("[6, 7, 8, 9, 10]");
+  }
+
+  @Test public void dropElementsWithNoAmountTest() {
+    assert elements.drop(0).toArrayList().toString().equals("[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]");
+  }
+
+  @Test public void dropElementsWithNegativeAmountTest() {
+    assert elements.drop(-1).toArrayList().toString().equals("[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]");
+  }
+
+  @Test public void dropElementsWithAmountHigherThanListSizeTest() {
+    assert elements.drop(20).toArrayList().toString().equals("[]");
+  }
+}

seq/src/test/java/com/jmonad/seq/SeqTakeTest.java

@@ -0,0 +1,25 @@
+package com.jmonad.seq;
+
+import org.junit.Test;
+
+public class SeqTakeTest {
+
+  private Integer[] numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+  private Seq<Integer> elements = new Seq<>(numbers);
+
+  @Test public void takeListElementsTest() {
+    assert elements.take(5).toArrayList().toString().equals("[1, 2, 3, 4, 5]");
+  }
+
+  @Test public void takeElementsWithNoAmountTest() {
+    assert elements.take(0).toArrayList().toString().equals("[]");
+  }
+
+  @Test public void takeElementsWithNegativeAmountTest() {
+    assert elements.take(-1).toArrayList().toString().equals("[]");
+  }
+
+  @Test public void takeElementsWithAmountHigherThanListSizeTest() {
+    assert elements.take(20).toArrayList().toString().equals("[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]");
+  }
+}