Understand how lambda works in java

HelloWorld.java

import java.util.Arrays;
import java.util.function.Function;
import java.util.function.IntConsumer;
public class HelloWorld{
// https://blogs.oracle.com/javamagazine/behind-the-scenes-how-do-lambda-expressions-really-work-in-java
// javac .\HelloWorld.java 
// javap -p -c HelloWorld$1
    String sum="";
    public static void main(String []args){
        new HelloWorld().main(); //comment then uncomment below comments also
    } //comment
     public void main(){ // comment
        System.out.println("Hello World");
        int[] values={1,2,3};
        Arrays.stream(values).forEach(a->{
            // sum+=a;
            System.out.println(sum + a);
        });
        Arrays.stream(values).forEach(a->{
            // sum+=a;
            System.out.println("sum2");
        });
        
        Arrays.stream(values).forEach(new IntConsumer(){
            @Override
            public void accept(int t) {
                System.out.println("sum3");
            }
        });
        
        Arrays.stream(values).forEach(new IntConsumer(){
            @Override
            public void accept(int t) {
                sum+=" hi";
                        System.out.println(sum);
                System.out.println("sum3");
            }
        });
        
        // Arrays.stream(values).forEach((IntConsumer) new Function<Integer,Void>(){
        //     @Override
        //     public Void apply(Integer t) {
        //         System.out.println(sum);
        //         return null;
        //     }
        // });
     }
}