MainNullCheck.java

package examples;

import java.util.Optional;
import java.util.function.Supplier;

public class MainNullCheck {

 public static <T> Optional<T> resolve(Supplier<T> resolver) {
 try {
 T result = resolver.get();
 return Optional.ofNullable(result);
 } catch (NullPointerException e) {
 return Optional.empty();
 }
 }

 public static void main(String[] args) {
 Outer outer = new Outer();
 Outer obj = new Outer();
 Nested nested = new Nested();
 Inner inner = new Inner();
 nested.setInner(inner);
 outer.setNested(nested);

 //traditional way
 System.out.println("In the traditional check");
 if (outer != null && outer.getNested() != null && outer.getNested().getInner() != null) {
 System.out.println(outer.getNested().getInner().getFoo());
 }

 //Using java8 Optional type
 // map accepts a lambda expression of type Function and wraps each function result into an Optional
 // Null checks are automatically handled under the hood
 System.out.println("In the Optional");
 Optional.of(outer)
 .map(Outer::getNested)
 .map(Nested::getInner)
 .map(Inner::getFoo)
 .ifPresent(System.out::println);

 //Alternative way using Supplier function
 System.out.println("Using Supplier function");
 resolve(() -> outer.getNested().getInner().getFoo())
 .ifPresent(System.out::println);
 resolve(() -> obj.getNested().getInner().getFoo())
 .ifPresent(System.out::println);
 }

}