"package com.api does not exist".

import com.api.APIUser;
 public class Test{
  APIUser ap = new APIUser();
  ap .login();
  public static void main(String[] args){
    //to do
  }

}

package com.api
public class APIUser{
  public string login(){
   //to do
   return string;
 }

}

import com.api.APIUser;

public class Test {
    // APIUser ap = new APIUser(); // This call should be in the method body,
    // there is no use to keep it at the class level
    // ap.login(); // This call should be in method body
    public static void main(String[] args) {
        // TO DO
        APIUser ap = new APIUser();
        ap.login();
    }
}

package com.api; // added termination here

public class APIUser {
    //access specifier should be public
    public string login(){
       //to do
       //return string;//return some value from here, since string is not present this will lead to error
         return "string";
     }
}