How to do dependency injection

Example.java

//This Dependency class will be our main class.

public class Dependency implements Dependable{
  //Create a Dependent object using the instance of this dependency in the constructor
  private final Dependent dependent = new Dependent(this);
  
  //Create an OtherDependent object using the instance of this dependency in the constructor
  private final OtherDependent otherDependent = new OtherDependent(this);
  
  //Create an OtherDependent object using the instance of the dependent object in the constructor
  private final OtherDependent dependsDependent = new OtherDependent(dependent);
  
  public static void main(String[] args){
    //Call all the Dependable methods
    dependent.doSomething();
    otherDependent.doSomething();
    dependsDependent.doSometing();
  }

  //This method overrides from the Dependable interface
  @Override
  public void doSomething(){
    System.out.println("Hey, you did something!");
  }
  
  public static interface Dependable{
    public void doSomething();
  }
  
  public static class Dependent implements Dependable{
    //The Dependency object stored as a field of this Dependent object
    private final Dependency dependency;
  
    public Dependent(Dependency dependency){
      //Assign the dependency field using the value from the constructor
      this.dependency = dependency;
    }
  
    @Override
    public void doSomething(){
      //Add custom behavior to the doSomething method, and call the method from Dependency
      System.out.println("This was called from Dependent.java!");
      dependency.doSomething();
    }
  }
  
  public static class OtherDependent implements Dependable{
    //This class accepts any Dependable object to function as a dependency
    private final Dependable dependency;
  
    public OtherDependent(Dependable dependency){
      //Dependency assignment via constructor
      this.dependency = dependency;
    }
  
    @Override
    public void doSomething(){
      //Custom doSomething behavior as well as calling method from dependency
      System.out.println("This was called from OtherDependent.java!");
      dependency.doSomething();
    }
  }
}