BAEL-906 code for min max priority queue and evicting queue (#1827)

* BAEL-906 code for min max priority queue and evicting queue

* BAEL-906 simplify example

* BAEL-906 test method renamed

guava/src/test/java/org/baeldung/guava/EvictingQueueTest.java

@@ -0,0 +1,31 @@
+package org.baeldung.guava;
+
+
+import com.google.common.collect.EvictingQueue;
+import org.junit.Test;
+
+import java.util.Queue;
+import java.util.stream.IntStream;
+
+import static org.assertj.core.api.Java6Assertions.assertThat;
+
+public class EvictingQueueTest {
+
+    @Test
+    public void givenEvictingQueue_whenAddElementToFull_thenShouldEvictOldestItem() {
+        //given
+        Queue<Integer> evictingQueue = EvictingQueue.create(10);
+
+        //when
+        IntStream.range(0, 10).forEach(evictingQueue::add);
+
+        //then
+        assertThat(evictingQueue).containsExactly(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
+
+        //and
+        evictingQueue.add(100);
+
+        //then
+        assertThat(evictingQueue).containsExactly(1, 2, 3, 4, 5, 6, 7, 8, 9, 100);
+    }
+}

guava/src/test/java/org/baeldung/guava/MinMaxPriorityQueueTest.java

@@ -0,0 +1,66 @@
+package org.baeldung.guava;
+
+
+import com.google.common.collect.MinMaxPriorityQueue;
+import org.junit.Test;
+
+import java.util.Comparator;
+import java.util.stream.IntStream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class MinMaxPriorityQueueTest {
+    @Test
+    public void givenMinMaxPriorityQueue_whenAddElementToFull_thenShouldEvictGreatestItem() {
+        //given
+        MinMaxPriorityQueue<CustomClass> queue = MinMaxPriorityQueue
+                .orderedBy(Comparator.comparing(CustomClass::getValue))
+                .maximumSize(10)
+                .create();
+
+        //when
+        IntStream
+                .iterate(10, i -> i - 1)
+                .limit(10)
+                .forEach(i -> queue.add(new CustomClass(i)));
+
+        //then
+        assertThat(queue.peekFirst().getValue()).isEqualTo(1);
+        assertThat(queue.peekLast().getValue()).isEqualTo(10);
+
+
+        //and
+        queue.add(new CustomClass(-1));
+
+
+        //then
+        assertThat(queue.peekFirst().getValue()).isEqualTo(-1);
+        assertThat(queue.peekLast().getValue()).isEqualTo(9);
+
+        //and
+        queue.add(new CustomClass(100));
+        assertThat(queue.peekFirst().getValue()).isEqualTo(-1);
+        assertThat(queue.peekLast().getValue()).isEqualTo(9);
+
+    }
+
+
+    class CustomClass {
+        private final Integer value;
+
+        CustomClass(Integer value) {
+            this.value = value;
+        }
+
+        public Integer getValue() {
+            return value;
+        }
+
+        @Override
+        public String toString() {
+            return "CustomClass{" +
+                    "value=" + value +
+                    '}';
+        }
+    }
+}