techindepth

Foo foo = parameter -> buildString(parameter);

private String buildString(String parameter) {
    String result = "Something " + parameter;
    //many lines of code
    return result;
}

techindepth

public String scopeExperiment() {
    Foo fooIC = new Foo() {
        String value = "Inner class value";
 
        @Override
        public String method(String string) {
            return this.value;
        }
    };
    String resultIC = fooIC.method("");

techindepth

public interface Adder {
    String add(Function<String, String> f);
    void add(Consumer<Integer> f);
}
 
public class AdderImpl implements Adder {
 
    @Override
    public  String add(Function<String, String> f) {
        return f.apply("Something ");

techindepth

Foo fooByIC = new Foo() {
    @Override
    public String method(String string) {
        return string + " from Foo";
    }
};

techindepth

@FunctionalInterface
public interface FooExtended extends Baz, Bar {}
     
@FunctionalInterface
public interface Baz {  
    String method();    
    default void defaultBaz() {}        
}
     
@FunctionalInterface

techindepth

@FunctionalInterface
public interface Foo {
    String method();
    default void defaultMethod() {}
}

techindepth

public interface Foo {
    String method();
}

techindepth

@FunctionalInterface
public interface Foo {
    String method();
}

techindepth

// Java program with Optional Class 
import java.util.Optional;   
public class OptionalDemo{   
    public static void main(String[] args) {   
        String[] words = new String[10];   
        Optional<String> checkNull =  
                      Optional.ofNullable(words[5]);   
        if (checkNull.isPresent()) {   
            String word = words[5].toLowerCase();   
            System.out.print(word);   

techindepth

// Java program without Optional Class 
public class OptionalDemo{   
    public static void main(String[] args) {   
        String[] words = new String[10];   
        String word = words[5].toLowerCase();   
        System.out.print(word);   
    }   
}