JavaBeans require a no-argument constructor to be present.
When a Java class has no constructors at all, there is a default no-arg constructor automatically added to it by the compiler. The moment you define any constructor in the class, the default no-arg constructor goes away.
In your code, your users class defines such a constructor that contains arguments:
public users(String user_id, String address, String contact,String name)
{}
As long as that constructor is present, and you don't define a no-arg constructor, that class will not have one.
To resolve this, you either need to remove that constructor from the class, or manually add a no-arg constructor to it:
public users() {}
