java optional code example

Example 1: check if optional is empty java

@Test
public void givenNull_whenCreatesNullable_thenCorrect() {
    String name = null;
    Optional<String> opt = Optional.ofNullable(name);
    assertFalse(opt.isPresent());
}

Example 2: instantiate optinal java 8

Person p = new Person();
Optional<Person> op = Optional.of(p);

Example 3: check if optional is empty java

String o = getOptional().orElse(null);
if (o == null) {
    return;
}

Example 4: java how to make a parameter optional

void foo(String a, Integer b) {
    //...
}

void foo(String a) {
    foo(a, 0); // here, 0 is a default value for b
}

foo("a", 2);
foo("a");

Example 5: java how to make a parameter optional

class Foo {
     private final String a; 
     private final Integer b;

     Foo(String a, Integer b) {
       this.a = a;
       this.b = b;
     }

     //...
 }

 class FooBuilder {
   private String a = ""; 
   private Integer b = 0;

   FooBuilder setA(String a) {
     this.a = a;
     return this;
   }

   FooBuilder setB(Integer b) {
     this.b = b;
     return this;
   }

   Foo build() {
     return new Foo(a, b);
   }
 }

 Foo foo = new FooBuilder().setA("a").build();