hibernate model object

I was going through below 2 ways of declaring model object

package org.gp.gpr.dto;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;

//import org.hibernate.annotations.Entity;

@Entity(name="USER_DETAILS")
public class UserDetails {

private int userId;
@Id
@Column(name="USER_ID")
public int getUserId() {
      return userId;
}
public void setUserId(int userId) {
      this.userId = userId;
}
@Column(name="USER_NAME")
public String getUserName() {
      return userName+"from get";
}
public void setUserName(String userName) {
      this.userName = userName;
}

private String userName;
}









package org.gp.gpr.dto;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;

//import org.hibernate.annotations.Entity;

@Entity

@Table(name="USER_DETAILS")
public class UserDetails {

private int userId;
@Id
@Column(name="USER_ID")
public int getUserId() {
      return userId;
}
public void setUserId(int userId) {
      this.userId = userId;
}
@Column(name="USER_NAME")
public String getUserName() {
      return userName+"from get";
}
public void setUserName(String userName) {
      this.userName = userName;
}

private String userName;
}

I did not understood the difference. Which one to use where and uses.

@Entity(name="USER_DETAILS")
public class UserDetails {

private int userId;
@Id



then below

@Entity

@Table(name="USER_DETAILS")
public class UserDetails {

private int userId;
@Id



Please advise. Any ideas, resources, sample code highly appreciated. thanks in advance