JAVA學習-第二個代碼模型

標籤：

第二個模型: 資料表與簡單java類映射

題目要求，要求使用emp表（empno、ename、job、sal、comm、mgr、deptno）和dept（deptno、dname、loc）表進行操作，要求可以實現如下的功能：

                   · 功能一：可以輸出部門的完整資訊，同時輸出部門之中所有僱員以及僱員直接領導的資訊；

                   · 功能二：可以根據一個僱員找到僱員的領導資訊和他所在的部門資訊。

         在本程式之中有兩個關聯的對應關係：

                   · 關係一：僱員和部門之間依靠的deptno欄位的聯絡；

                   · 關係二：僱員和領導之間的聯絡，依靠mgr欄位。

步驟一：編寫簡單Java類，暫時只包含表之中的基本欄位。

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 "僱員編號：" + this.empno + "，姓名：" + this.ename + "，職位：" + this.job + "，工資：" + this.sal + "，傭金：" + 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 "部門編號：" + this.deptno + "，名稱：" + this.dname + "，位置：" + this.loc ;          } }

步驟二：設定關係欄位

         · 一對多關聯性：部門和僱員；

         · 一對一關聯性：僱員和領導。

class Emp {          private int empno ;          private String ename ;          private String job ;          private double sal ;          private double comm ;          private Dept dept ;        // 一個僱員屬於一個部門          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 "僱員編號：" + this.empno + "，姓名：" + this.ename + "，職位：" + this.job + "，工資：" + this.sal + "，傭金：" + this.comm ;          } } class Dept {          private int deptno ;          private String dname ;          private String loc ;          private Emp emps [] ;   // 多個僱員          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 "部門編號：" + this.deptno + "，名稱：" + this.dname + "，位置：" + this.loc ;          } }

步驟三：按照表結構設定資料，同時設定完資料後按照表結構取出

public class TestDemo {          public static void main(String args[]) {                    // 第一層次：設定關係                    // 1、分別設定個個對象實體，彼此之間沒有聯絡                    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(10,"ACCOUNTING","New York") ;                    // 2、設定僱員和領導關係                    ea.setMgr(eb) ;                    eb.setMgr(ec) ;    // ec沒有領導                    // 3、設定僱員和部門關係                    ea.setDept(dept) ;          // 僱員和部門                    eb.setDept(dept) ;         // 僱員和部門                    ec.setDept(dept) ;          // 僱員和部門                    Emp [] temp = new Emp[] {ea,eb,ec} ;                    dept.setEmps(temp) ;                    // 第二層次：根據關係取資料                    // 1、取出部門資訊                    System.out.println(dept.getInfo()) ;                    // 2、取出部門之中的所有僱員資訊                    Emp [] allEmps = dept.getEmps() ; // 先接收                    for (int x = 0 ; x < allEmps.length ; x ++) {                             Emp e = allEmps[x] ;    // 取出一個僱員                             System.out.println("\t" + e.getInfo()) ;                             if (e.getMgr() != null) {         // 有領導                                      System.out.println("\t\t|- " + e.getMgr().getInfo()) ;                             }                    }                    // 3、根據僱員取資訊                    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()) ;                    }          } }

         在今天學習完之後，必須具備這種簡單java類與資料錶轉換的能力。

JAVA學習-第二個代碼模型