BAEL-1584 : Finding an element in list (eugenp#4067)

* BAEL-1584 : Find an Element in Given List

core-java-8/src/main/java/com/baeldung/findanelement/Customer.java

@@ -0,0 +1,37 @@
+package com.baeldung.findanelement;
+
+public class Customer {
+
+    private int id;
+    private String name;
+
+    public Customer(int id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    @Override
+    public int hashCode() {
+        return id * 20;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof Customer) {
+            Customer otherCustomer = (Customer) obj;
+            if (id == otherCustomer.id)
+                return true;
+        }
+        return false;
+    }
+
+
+}

core-java-8/src/main/java/com/baeldung/findanelement/FindACustomerInGivenList.java

@@ -0,0 +1,77 @@
+package com.baeldung.findanelement;
+
+import java.util.Iterator;
+import java.util.List;
+
+import org.apache.commons.collections4.IterableUtils;
+
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
+
+public class FindACustomerInGivenList {
+
+    public Customer findUsingGivenIndex(int indexOfCustomer, List<Customer> customers) {
+        if (indexOfCustomer >= 0 && indexOfCustomer < customers.size())
+            return customers.get(indexOfCustomer);
+        return null;
+    }
+
+    public int findUsingIndexOf(Customer customer, List<Customer> customers) {
+        return customers.indexOf(customer);
+    }
+
+    public boolean findUsingContains(Customer customer, List<Customer> customers) {
+        return customers.contains(customer);
+    }
+
+    public Customer findUsingIterator(String name, List<Customer> customers) {
+        Iterator<Customer> iterator = customers.iterator();
+        while (iterator.hasNext()) {
+            Customer customer = iterator.next();
+            if (customer.getName().equals(name)) {
+                return customer;
+            }
+        }
+        return null;
+    }
+
+    public Customer findUsingEnhancedForLoop(String name, List<Customer> customers) {
+        for (Customer customer : customers) {
+            if (customer.getName().equals(name)) {
+                return customer;
+            }
+        }
+        return null;
+    }
+
+    public Customer findUsingStream(String name, List<Customer> customers) {
+        return customers.stream()
+            .filter(customer -> customer.getName().equals(name))
+            .findFirst()
+            .orElse(null);
+    }
+
+    public Customer findUsingParallelStream(String name, List<Customer> customers) {
+        return customers.parallelStream()
+            .filter(customer -> customer.getName().equals(name))
+            .findAny()
+            .orElse(null);
+    }
+
+    public Customer findUsingGuava(String name, List<Customer> customers) {
+        return Iterables.tryFind(customers, new Predicate<Customer>() {
+            public boolean apply(Customer customer) {
+                return customer.getName().equals(name);
+            }
+        }).orNull();
+    }
+
+    public Customer findUsingApacheCommon(String name, List<Customer> customers) {
+        return IterableUtils.find(customers, new org.apache.commons.collections4.Predicate<Customer>() {
+            public boolean evaluate(Customer customer) {
+                return customer.getName().equals(name);
+            }
+        });
+    }
+
+}

core-java-8/src/test/java/com/baeldung/findanelement/FindACustomerInGivenListTest.java

@@ -0,0 +1,158 @@
+package com.baeldung.findanelement;
+
+import static org.junit.Assert.*;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+
+public class FindACustomerInGivenListTest {
+
+    private static List<Customer> customers = new ArrayList<>();
+
+    static {
+        customers.add(new Customer(1, "Jack"));
+        customers.add(new Customer(2, "James"));
+        customers.add(new Customer(3, "Sam"));
+    }
+
+    private static FindACustomerInGivenList findACustomerInGivenList = new FindACustomerInGivenList();
+
+    @Test
+    public void givenAnIndex_whenFoundUsingGivenIndex_thenReturnCustomer() {
+        Customer customer = findACustomerInGivenList.findUsingGivenIndex(0, customers);
+
+        assertEquals(1, customer.getId());
+    }
+
+    @Test
+    public void givenAnIndex_whenNotFoundUsingGivenIndex_thenReturnNull() {
+        Customer customer = findACustomerInGivenList.findUsingGivenIndex(5, customers);
+
+        assertNull(customer);
+    }
+
+    @Test
+    public void givenACustomer_whenFoundUsingContains_thenReturnTrue() {
+        Customer james = new Customer(2, "James");
+        boolean isJamesPresent = findACustomerInGivenList.findUsingContains(james, customers);
+
+        assertEquals(true, isJamesPresent);
+    }
+
+    @Test
+    public void givenACustomer_whenNotFoundUsingContains_thenReturnFalse() {
+        Customer john = new Customer(5, "John");
+        boolean isJohnPresent = findACustomerInGivenList.findUsingContains(john, customers);
+
+        assertEquals(false, isJohnPresent);
+    }
+
+    @Test
+    public void givenACustomer_whenFoundUsingIndexOf_thenReturnItsIndex() {
+        Customer james = new Customer(2, "James");
+        int indexOfJames = findACustomerInGivenList.findUsingIndexOf(james, customers);
+
+        assertEquals(1, indexOfJames);
+    }
+
+    @Test
+    public void givenACustomer_whenNotFoundUsingIndexOf_thenReturnMinus1() {
+        Customer john = new Customer(5, "John");
+        int indexOfJohn = findACustomerInGivenList.findUsingIndexOf(john, customers);
+
+        assertEquals(-1, indexOfJohn);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingIterator_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingIterator("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingIterator_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingIterator("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingEnhancedFor_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingEnhancedForLoop("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingEnhancedFor_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingEnhancedForLoop("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingStream_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingStream("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingStream_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingStream("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingParallelStream_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingParallelStream("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingParallelStream_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingParallelStream("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingApacheCommon_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingApacheCommon("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingApacheCommon_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingApacheCommon("John", customers);
+
+        assertNull(john);
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameFoundUsingGuava_thenReturnCustomer() {
+        Customer james = findACustomerInGivenList.findUsingGuava("James", customers);
+
+        assertEquals("James", james.getName());
+        assertEquals(2, james.getId());
+    }
+
+    @Test
+    public void givenName_whenCustomerWithNameNotFoundUsingGuava_thenReturnNull() {
+        Customer john = findACustomerInGivenList.findUsingGuava("John", customers);
+
+        assertNull(john);
+    }
+
+}