Java Learning-a second code model

Second model: Data tables and simple Java class mappings

Required to use the EMP table (empno,ename,job,sal, Comm,Mgr,deptno) and dept (Deptno, dname, loc) tables are required to perform the following functions:

· Function One: The complete information of the department can be exported, and the information of all employees and employees in the department will be exported.

· Function Two: can be based on an employee to find the employee's leadership information and his department information.

There are two related relationships in this program:

· Relationship one: The relation between the employee and the department depends on the Deptno field;

· Relationship two: The link between employees and leaders, relying on the Mgr field.

Step One: Write a simple Java class that temporarily contains only the basic fields in the table.

Class Emp { private int empno; Private String ename; Private String job; Private double Sal; Private double comm; Public Emp () {} Public Emp (int empno,string ename,string job,double sal,double comm) { This.empno = empno; This.ename = ename; This.job = job; This.sal = sal; This.comm = comm; } Public String GetInfo () { Return "Employee Number:" + This.empno + ", Name:" + This.ename + ", Position:" + this.job + ", Salary:" + this.sal + ", Commission:" + This.comm; } } Class Dept { private int deptno; Private String dname; Private String Loc; Public Dept () {} Public Dept (int deptno,string dname,string loc) { This.deptno = Deptno; This.dname = dname; This.loc = loc; } Public String GetInfo () { Return "department Number:" + This.deptno + ", Name:" + this.dname + ", Location:" + this.loc; } }

Step Two: Set the Relationship field

· One-to-many relationships: departments and employees;

· One-to-one relationships: employees and leaders.

Class Emp { private int empno; Private String ename; Private String job; Private double Sal; Private double comm; Private Dept Dept; An employee belongs to a department Private EMP Mgr; Public Emp () {} Public Emp (int empno,string ename,string job,double sal,double comm) { This.empno = empno; This.ename = ename; This.job = job; This.sal = sal; This.comm = comm; } public void Setmgr (Emp Mgr) { This.mgr = Mgr; } Public Emp Getmgr () { return this.mgr; } public void Setdept (Dept Dept) { this.dept = Dept; } Public Dept getdept () { return this.dept; } Public String GetInfo () { Return "Employee Number:" + This.empno + ", Name:" + This.ename + ", Position:" + this.job + ", Salary:" + this.sal + ", Commission:" + This.comm; } } Class Dept { private int deptno; Private String dname; Private String Loc; Private EMP Emps []; Multiple employees Public Dept () {} Public Dept (int deptno,string dname,string loc) { This.deptno = Deptno; This.dname = dname; This.loc = loc; } public void Setemps (EMP emps[]) { This.emps = Emps; } Public EMP [] Getemps () { return this.emps; } Public String GetInfo () { Return "department Number:" + This.deptno + ", Name:" + this.dname + ", Location:" + this.loc; } }

Step Three: set the data according to the table structure, and set the data after the table structure to remove

public class Testdemo { public static void Main (String args[]) { First level: Setting up relationships 1. Set each object entity separately, no connection between each other EMP ea = new EMP (7369, "SMITH", "clerk", 800.0,0.0); EMP EB = new emp (7902, "FORD", "MANAGER", 2450.0,0.0); EMP EC = new EMP (7839, "KING", "President", 5000.0,0.0); Dept Dept = new Dept ("ACCOUNTING", "New York"); 2. Setting up employees and leadership relationships Ea.setmgr (EB); Eb.setmgr (EC); EC does not lead 3. Set up employee and departmental relationships Ea.setdept (dept); Employees and Departments Eb.setdept (dept); Employees and Departments Ec.setdept (dept); Employees and Departments EMP [] temp = new emp[] {EA,EB,EC}; Dept.setemps (temp); Second level: Take data based on relationship 1. Remove Department information System.out.println (Dept.getinfo ()); 2. Remove all employee information from the department EMP [] allemps = Dept.getemps (); Receive first for (int x = 0; x < allemps.length; x + +) { Emp e = allemps[x]; Take out an employee System.out.println ("\ T" + e.getinfo ()); if (e.getmgr () = null) {//has a leader System.out.println ("\t\t|-" + e.getmgr (). GetInfo ()); } } 3, according to employees to take information System.out.println (Ea.getinfo ()); if (ea.getmgr () = null) { System.out.println (Ea.getmgr (). GetInfo ()); } if (ea.getdept () = null) { System.out.println (Ea.getdept (). GetInfo ()); } } }

After today's study, you have to have this simple Java class and data table conversion capabilities.

Java Learning-a second code model