Merge pull request #6153 from cror/stream-count

BAEL-2546: Stream.count

java-streams/src/main/java/com/baeldung/stream/filter/Customer.java

@@ -32,7 +32,7 @@ public class Customer {
         return this.points > points;
     }
 
-    public boolean hasOverThousandPoints() {
+    public boolean hasOverHundredPoints() {
         return this.points > 100;
     }
 

java-streams/src/test/java/com/baeldung/stream/filter/StreamCountUnitTest.java

@@ -0,0 +1,72 @@
+package com.baeldung.stream.filter;
+
+import org.junit.Test;
+import org.junit.Before;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class StreamCountUnitTest {
+
+    private List<Customer> customers;
+
+    @Before
+    public void setUp() {
+        Customer john = new Customer("John P.", 15, "https://images.unsplash.com/photo-1543320485-d0d5a49c2b2e");
+        Customer sarah = new Customer("Sarah M.", 200);
+        Customer charles = new Customer("Charles B.", 150);
+        Customer mary = new Customer("Mary T.", 1, "https://images.unsplash.com/photo-1543297057-25167dfc180e");
+        customers = Arrays.asList(john, sarah, charles, mary);
+    }
+
+    @Test
+    public void givenListOfCustomers_whenCount_thenGetListSize() {
+        long count = customers
+          .stream()
+          .count();
+
+        assertThat(count).isEqualTo(4L);
+    }
+
+    @Test
+    public void givenListOfCustomers_whenFilterByPointsOver100AndCount_thenGetTwo() {
+        long countBigCustomers = customers
+          .stream()
+          .filter(c -> c.getPoints() > 100)
+          .count();
+
+        assertThat(countBigCustomers).isEqualTo(2L);
+    }
+
+    @Test
+    public void givenListOfCustomers_whenFilterByPointsAndNameAndCount_thenGetOne() {
+        long count = customers
+          .stream()
+          .filter(c -> c.getPoints() > 10 && c.getName().startsWith("Charles"))
+          .count();
+
+        assertThat(count).isEqualTo(1L);
+    }
+
+    @Test
+    public void givenListOfCustomers_whenNoneMatchesFilterAndCount_thenGetZero() {
+        long count = customers
+          .stream()
+          .filter(c -> c.getPoints() > 500)
+          .count();
+
+        assertThat(count).isEqualTo(0L);
+    }
+
+    @Test
+    public void givenListOfCustomers_whenUsingMethodOverHundredPointsAndCount_thenGetTwo() {
+        long count = customers
+          .stream()
+          .filter(Customer::hasOverHundredPoints)
+          .count();
+
+        assertThat(count).isEqualTo(2L);
+    }
+}

java-streams/src/test/java/com/baeldung/stream/filter/StreamFilterUnitTest.java

@@ -62,7 +62,7 @@ public class StreamFilterUnitTest {
 
         List<Customer> customersWithMoreThan100Points = customers
           .stream()
-          .filter(Customer::hasOverThousandPoints)
+          .filter(Customer::hasOverHundredPoints)
           .collect(Collectors.toList());
 
         assertThat(customersWithMoreThan100Points).hasSize(2);
@@ -81,7 +81,7 @@ public class StreamFilterUnitTest {
           .flatMap(c -> c
             .map(Stream::of)
             .orElseGet(Stream::empty))
-          .filter(Customer::hasOverThousandPoints)
+          .filter(Customer::hasOverHundredPoints)
           .collect(Collectors.toList());
 
         assertThat(customersWithMoreThan100Points).hasSize(2);
@@ -156,4 +156,5 @@ public class StreamFilterUnitTest {
           })
           .collect(Collectors.toList())).isInstanceOf(RuntimeException.class);
     }
+    
 }