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Author: basahota

Optional/Customer.java

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+package com.javatechie;
+
+import java.util.List;
+import java.util.Optional;
+
+public class Customer {
+
+    private int id;
+    private String name;
+    private String email;
+    private List<String> phoneNumbers;
+
+    public Customer() {
+    }
+
+    public Customer(int id, String name, String email, List<String> phoneNumbers) {
+        this.id = id;
+        this.name = name;
+        this.email = email;
+        this.phoneNumbers = phoneNumbers;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Optional<String> getEmail() {
+        return Optional.ofNullable(email);
+    }
+
+    public void setEmail(String email) {
+        this.email = email;
+    }
+
+    public List<String> getPhoneNumbers() {
+        return phoneNumbers;
+    }
+
+    public void setPhoneNumbers(List<String> phoneNumbers) {
+        this.phoneNumbers = phoneNumbers;
+    }
+}

Optional/EkartDataBase.java

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+package com.javatechie;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+public class EkartDataBase {
+
+
+    public static List<Customer> getAll() {
+        return Stream.of(
+                new Customer(101, "john", "[email protected]", Arrays.asList("397937955", "21654725")),
+                new Customer(102, "smith", "[email protected]", Arrays.asList("89563865", "2487238947")),
+                new Customer(103, "peter", "[email protected]", Arrays.asList("38946328654", "3286487236")),
+                new Customer(104, "kely", "[email protected]", Arrays.asList("389246829364", "948609467"))
+        ).collect(Collectors.toList());
+    }
+
+
+}

Optional/OptionalDemo.java

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+package com.javatechie;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+public class OptionalDemo {
+
+
+
+    public static Customer getCustomerByEmailId(String email) throws Exception {
+        List<Customer> customers = EkartDataBase.getAll();
+       return customers.stream()
+                .filter(customer -> customer.getEmail().equals(email))
+                .findAny().orElseThrow(()->new Exception("no customer present with this email id"));
+
+    }
+
+    public static void main(String[] args) throws Exception {
+
+        Customer customer=new Customer(101, "john", "[email protected]", Arrays.asList("397937955", "21654725"));
+
+        //empty
+        //of
+        //ofNullable
+
+        Optional<Object> emptyOptional = Optional.empty();
+        System.out.println(emptyOptional);
+
+        //Optional<String> emailOptional = Optional.of(customer.getEmail());
+        //System.out.println(emailOptional);
+
+        Optional<String> emailOptional2 = Optional.ofNullable(customer.getEmail());
+       /* if(emailOptional2.isPresent()){
+            System.out.println(emailOptional2.get());
+        }*/
+       // System.out.println(emailOptional2.orElse("[email protected]"));
+
+       // System.out.println(emailOptional2.orElseThrow(()->new IllegalArgumentException("email not present")));
+
+
+        System.out.println(emailOptional2.map(String::toUpperCase).orElseGet(()->"default email..."));
+
+        getCustomerByEmailId("pqr");
+    }
+}