java - getDeclaredConstructors() lists 2 constructors but there is only one -

given little pice of code:

import java.util.arrays;  public class sample {     private final int test;      private sample(int test) {         this.test = test;     }      public static void main(string[] args) {         system.out.println(arrays.tostring(hello.class.getdeclaredconstructors()));     }      public static class hello {         private final int i;          private hello(int i) {             this.i = i;         }          public int geti() {             return i;         }          public static class builder {             private int i;              private builder() {              }              public static builder builder() {                 return new builder();             }              public void add(int i) {                 this.i = i;             }              public hello build() {                 return new hello(i);             }         }     } } 

i don't understand output shown:

[private sample$hello(int), sample$hello(int,sample$1)] 

what second listed constructor in here second parameter builder. thought output show private constructor of hello not second one.

builder static nested class of hello, therefore should able access private constructor sample$hello(int).

however, jvm doesn't have special support nested classes, therefore, jvm point of view, builder cannot access sample$hello(int).

in order solve problem compiler generates synthetic constructor sample$hello(int,sample$1) default visibility, , calls instead of sample$hello(int) builder.

sample$1 empty class generated compiler make distinguished signature sample$hello(int,sample$1). actually, second argument of constructor null.