Add new methods: first(list, predicate), firstOrNull(list),

firstOrNull(list, predicate), last(list, predicate), lastOrNull(list),
lastOrNull(list, predicate).

Author: javadev

src/main/java/com/github/underscore/$.java

@@ -732,6 +732,34 @@ public List<T> first(final int n) {
         return ((List) iterable).subList(0, n);
     }
 
+    public static <E> E first(final Iterable<E> iterable, final Predicate<E> pred) {
+        return filter(newArrayList(iterable), pred).iterator().next();
+    }
+
+    public T first(final Predicate<T> pred) {
+        return filter(newArrayList(iterable), pred).iterator().next();
+    }
+
+    public static <E> E firstOrNull(final Iterable<E> iterable) {
+        final Iterator<E> iterator = iterable.iterator();
+        return iterator.hasNext() ? iterator.next() : null;
+    }
+
+    public T firstOrNull() {
+        final Iterator<T> iterator = iterable.iterator();
+        return iterator.hasNext() ? iterator.next() : null;
+    }
+
+    public static <E> E firstOrNull(final Iterable<E> iterable, final Predicate<E> pred) {
+        final Iterator<E> iterator = filter(newArrayList(iterable), pred).iterator();
+        return iterator.hasNext() ? iterator.next() : null;
+    }
+
+    public T firstOrNull(final Predicate<T> pred) {
+        final Iterator<T> iterator = filter(newArrayList(iterable), pred).iterator();
+        return iterator.hasNext() ? iterator.next() : null;
+    }
+
     public static <E> E head(final Iterable<E> iterable) {
         return first(iterable);
     }
@@ -802,6 +830,32 @@ public List<T> last(final int n) {
         return last((List) iterable, n);
     }
 
+    public static <E> E last(final List<E> list, final Predicate<E> pred) {
+        final List<E> filteredList = filter(list, pred);
+        return filteredList.get(filteredList.size() - 1);
+    }
+
+    public T last(final Predicate<T> pred) {
+        return last((List<T>) iterable, pred);
+    }
+
+    public static <E> E lastOrNull(final List<E> list) {
+        return list.isEmpty() ? null : list.get(list.size() - 1);
+    }
+
+    public T lastOrNull() {
+        return lastOrNull((List<T>) iterable);
+    }
+
+    public static <E> E lastOrNull(final List<E> list, final Predicate<E> pred) {
+        final List<E> filteredList = filter(list, pred);
+        return filteredList.isEmpty() ? null : filteredList.get(filteredList.size() - 1);
+    }
+
+    public T lastOrNull(final Predicate<T> pred) {
+        return lastOrNull((List<T>) iterable, pred);
+    }
+
     public static <E> List<E> rest(final List<E> list) {
         return rest(list, 1);
     }

src/test/java/com/github/underscore/ArraysTest.java

@@ -26,12 +26,14 @@
 import org.junit.Test;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.NoSuchElementException;
 
 import static java.util.Arrays.asList;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 
 /**
  * Underscore library unit test.
@@ -58,6 +60,50 @@ public void first() {
         assertEquals("[5, 4]", resultList.toString());
         final int resultInt = $.first(new Integer[] {5, 4, 3, 2, 1});
         assertEquals(5, resultInt);
+        final int resultPred = $.first(asList(5, 4, 3, 2, 1), new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        });
+        assertEquals(4, resultPred);
+        final int resultPredObj = new $<Integer>(asList(5, 4, 3, 2, 1)).first(new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        });
+        assertEquals(4, resultPredObj);
+    }
+
+    @Test
+    public void firstOrNull() {
+        final Integer result = $.firstOrNull(asList(5, 4, 3, 2, 1));
+        assertEquals("5", result.toString());
+        final Integer resultObj = new $<Integer>(asList(5, 4, 3, 2, 1)).firstOrNull();
+        assertEquals("5", resultObj.toString());
+        assertNull($.firstOrNull(Collections.emptyList()));
+        assertNull(new $<Integer>(Collections.<Integer>emptyList()).firstOrNull());
+        final int resultPred = $.firstOrNull(asList(5, 4, 3, 2, 1), new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        });
+        assertEquals(4, resultPred);
+        assertNull($.firstOrNull(Collections.<Integer>emptyList(), new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        }));
+        final int resultPredObj = new $<Integer>(asList(5, 4, 3, 2, 1)).firstOrNull(new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        });
+        assertEquals(4, resultPredObj);
+        assertNull(new $<Integer>(Collections.<Integer>emptyList()).firstOrNull(new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        }));
     }
 
     @Test(expected = NoSuchElementException.class)
@@ -213,8 +259,51 @@ public void last() {
         assertEquals("last one item did not work", 5, res.intValue());
         List<Integer> resList = new $(asList(1, 2, 3, 4, 5)).last(3);
         assertEquals("last multi item did not wok", asList(3, 4, 5), resList);
+        final int resultPred = $.last(asList(5, 4, 3, 2, 1), new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        });
+        assertEquals(2, resultPred);
+        final int resultPredObj = new $<Integer>(asList(5, 4, 3, 2, 1)).last(new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        });
+        assertEquals(2, resultPredObj);
     }
 
+    @Test
+    public void lastOrNull() {
+        final Integer result = $.lastOrNull(asList(5, 4, 3, 2, 1));
+        assertEquals("1", result.toString());
+        final Integer resultObj = new $<Integer>(asList(5, 4, 3, 2, 1)).lastOrNull();
+        assertEquals("1", resultObj.toString());
+        assertNull($.lastOrNull(Collections.emptyList()));
+        assertNull(new $<Integer>(Collections.<Integer>emptyList()).lastOrNull());
+        final int resultPred = $.lastOrNull(asList(5, 4, 3, 2, 1), new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        });
+        assertEquals(2, resultPred);
+        assertNull($.lastOrNull(Collections.<Integer>emptyList(), new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        }));
+        final int resultPredObj = new $<Integer>(asList(5, 4, 3, 2, 1)).lastOrNull(new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        });
+        assertEquals(2, resultPredObj);
+        assertNull(new $<Integer>(Collections.<Integer>emptyList()).lastOrNull(new Predicate<Integer>() {
+            public Boolean apply(Integer item) {
+                return item % 2 == 0;
+            }
+        }));
+    }
 /*
 _.compact([0, 1, false, 2, '', 3]);
 => [1, 2, 3]