Merge pull request #2197 from eugenp/bael-965-collection-util

bael-965

libraries/src/main/java/com/baeldung/commons/collectionutil/Address.java

@@ -0,0 +1,47 @@
+package com.baeldung.commons.collectionutil;
+
+public class Address {
+
+    String locality;
+    String city;
+    String zip;
+
+    public String getLocality() {
+        return locality;
+    }
+
+    public void setLocality(String locality) {
+        this.locality = locality;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getZip() {
+        return zip;
+    }
+
+    public void setZip(String zip) {
+        this.zip = zip;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Address [locality=").append(locality).append(", city=").append(city).append(", zip=").append(zip).append("]");
+        return builder.toString();
+    }
+
+    public Address(String locality, String city, String zip) {
+        super();
+        this.locality = locality;
+        this.city = city;
+        this.zip = zip;
+    }
+
+}

libraries/src/main/java/com/baeldung/commons/collectionutil/Customer.java

@@ -0,0 +1,118 @@
+package com.baeldung.commons.collectionutil;
+
+public class Customer implements Comparable<Customer> {
+
+    Integer id;
+    String name;
+    Long phone;
+    String locality;
+    String city;
+    String zip;
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Long getPhone() {
+        return phone;
+    }
+
+    public void setPhone(Long phone) {
+        this.phone = phone;
+    }
+
+    public String getLocality() {
+        return locality;
+    }
+
+    public void setLocality(String locality) {
+        this.locality = locality;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getZip() {
+        return zip;
+    }
+
+    public void setZip(String zip) {
+        this.zip = zip;
+    }
+
+    public Customer(Integer id, String name, Long phone, String locality, String city, String zip) {
+        super();
+        this.id = id;
+        this.name = name;
+        this.phone = phone;
+        this.locality = locality;
+        this.city = city;
+        this.zip = zip;
+    }
+
+    public Customer(Integer id, String name, Long phone) {
+        super();
+        this.id = id;
+        this.name = name;
+        this.phone = phone;
+    }
+    
+    public Customer(String name) {
+        super();
+        this.name = name;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Customer other = (Customer) obj;
+        if (name == null) {
+            if (other.name != null)
+                return false;
+        } else if (!name.equals(other.name))
+            return false;
+        return true;
+    }
+
+    public int compareTo(Customer o) {
+        return this.name.compareTo(o.getName());
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder builder = new StringBuilder();
+        builder.append("Customer [id=").append(id).append(", name=").append(name).append(", phone=").append(phone).append("]");
+        return builder.toString();
+    }
+
+}

libraries/src/test/java/com/baeldung/commons/collections/CollectionUtilsGuideTest.java

@@ -0,0 +1,110 @@
+package com.baeldung.commons.collections;
+
+
+import com.baeldung.commons.collectionutil.Address;
+import com.baeldung.commons.collectionutil.Customer;
+import org.apache.commons.collections4.Closure;
+import org.apache.commons.collections4.CollectionUtils;
+import org.apache.commons.collections4.Predicate;
+import org.apache.commons.collections4.Transformer;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.*;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class CollectionUtilsGuideTest {
+
+
+    Customer customer1 = new Customer(1, "Daniel", 123456l, "locality1", "city1", "1234");
+    Customer customer4 = new Customer(4, "Bob", 456789l, "locality4", "city4", "4567");
+    List<Customer> list1, list2, list3, linkedList1;
+
+    @Before
+    public void setup() {
+        Customer customer2 = new Customer(2, "Fredrik", 234567l, "locality2", "city2", "2345");
+        Customer customer3 = new Customer(3, "Kyle", 345678l, "locality3", "city3", "3456");
+        Customer customer5 = new Customer(5, "Cat", 567890l, "locality5", "city5", "5678");
+        Customer customer6 = new Customer(6, "John", 678901l, "locality6", "city6", "6789");
+
+        list1 = Arrays.asList(customer1, customer2, customer3);
+        list2 = Arrays.asList(customer4, customer5, customer6);
+        list3 = Arrays.asList(customer1, customer2);
+
+        linkedList1 = new LinkedList<>(list1);
+    }
+    
+    @Test
+    public void givenList_whenAddIgnoreNull_thenNoNullAdded() {
+        CollectionUtils.addIgnoreNull(list1, null);
+        assertFalse(list1.contains(null));
+    }
+    
+    @Test
+    public void givenTwoSortedLists_whenCollated_thenSorted() {
+        List<Customer> sortedList = CollectionUtils.collate(list1, list2);
+        assertTrue(sortedList.get(0).getName().equals("Bob"));
+        assertTrue(sortedList.get(2).getName().equals("Daniel"));
+    }
+    
+    @Test
+    public void givenListOfCustomers_whenTransformed_thenListOfAddress() {
+        Collection<Address> addressCol = CollectionUtils.collect(list1, customer -> {
+            return new Address(customer.getLocality(), customer.getCity(), customer.getZip());
+        });
+        
+        List<Address> addressList = new ArrayList<>(addressCol);
+        assertTrue(addressList.size() == 3);
+        assertTrue(addressList.get(0).getLocality().equals("locality1"));
+    }
+    
+    @Test
+    public void givenCustomerList_WhenFiltered_thenCorrectSize() {
+        
+        boolean isModified = CollectionUtils.filter(linkedList1, customer -> Arrays.asList("Daniel","Kyle").contains(customer.getName()));
+        
+        //filterInverse does the opposite. It removes the element from the list if the Predicate returns true
+        //select and selectRejected work the same way except that they do not remove elements from the given collection and return a new collection 
+        
+        assertTrue(isModified && linkedList1.size() == 2);
+    }
+    
+    @Test
+    public void givenNonEmptyList_whenCheckedIsNotEmpty_thenTrue() {
+        List<Customer> emptyList = new ArrayList<>();
+        List<Customer> nullList = null;
+        
+        //Very handy at times where we want to check if a collection is not null and not empty too.
+        //isNotEmpty does the opposite. Handy because using ! operator on isEmpty makes it missable while reading
+        assertTrue(CollectionUtils.isNotEmpty(list1));
+        assertTrue(CollectionUtils.isEmpty(nullList));
+        assertTrue(CollectionUtils.isEmpty(emptyList));
+    }
+    
+    @Test
+    public void givenCustomerListAndASubcollection_whenChecked_thenTrue() {
+        assertTrue(CollectionUtils.isSubCollection(list3, list1));
+    }
+    
+    @Test
+    public void givenTwoLists_whenIntersected_thenCheckSize() {
+        Collection<Customer> intersection = CollectionUtils.intersection(list1, list3);
+        assertTrue(intersection.size() == 2);
+    }
+    
+    @Test
+    public void givenTwoLists_whenSubtracted_thenCheckElementNotPresentInA() {
+        Collection<Customer> result = CollectionUtils.subtract(list1, list3);
+        assertFalse(result.contains(customer1));
+    }
+    
+    @Test
+    public void givenTwoLists_whenUnioned_thenCheckElementPresentInResult() {
+        Collection<Customer> union = CollectionUtils.union(list1, list2);
+        assertTrue(union.contains(customer1));
+        assertTrue(union.contains(customer4));
+    }
+    
+}