Learning record 09 --- use the List collection to write a concise version of the local educational administration management system based on

Some time ago to write the educational management system uses a set of back-end, but was not too much to understand the role of the collection, but according to some information to use

What to know again the next through a simple set of local educational administration system in the end is

For convenience, I put all of them written in a class, we create a class of students directly by way of internal class is created

1  // by way of the class is created inside student class 
2      public  static  class Student {
 . 3          // temporarily create three properties, to be understood that the focus is set List 
. 4          public  int ID;
 . 5          public String name;
 . 6          public String pwd;
 . 7  
. 8          / / create a constructor 
. 9          public Student ( int ID, String name, String pwd) {
 10              the this .id = ID;
 . 11              the this .name = name;
 12 is              the this .pwd = pwd;
 13 is          }
 14 
15         //重写toString方法
16         @Override
17         public String toString() {
18             return "Student{" +
19                     "id=" + id +
20                     ", name='" + name + '\'' +
21                     ", pwd='" + pwd + '\'' +
22                     '}';
23         }
24     }

 

Once you have created inner class, we begin to create a set of global variables List, to say here, is definitely guide package util package, not awt package, otherwise there will be problems

// Create a List collection of global variables 
    static List <Student> List = new new ArrayList <Student> ();

Angle brackets Student representation is generic, this also can not give, do not give, then the default is the Object type, if given, they are all types Student

ArrayList is linear memory, we do educational management system with this is enough

Because the List collection has a complete CRUD methods, so we can put all the operations are written in the switch inside, of course, the work is not allowed to do so

Adding and queries are best done, add the add method can be used directly

// call the Add method to add data 
list.add ( new new Student (getInt ( "Please enter the Student ID:"), getString ( "Enter the student's name:"), getString ( "Please enter the password for the students:")));

This line of code can be resolved, the next query, use the foreach loop on the line

// use foreach loop through the collection 
for (Student info: List) { 
     PL (info.toString ()); 
}

But then, modify, and delete when using this two methods is to work through the index, so writing this two methods, we need to write a method to get at the underlying

1  // set the ID mark obtained according to 
2      public  static  int getIndexById ( int ID) {
 . 3          // used to access a variable subscript 
. 4          int index = 0 ;
 . 5          // traversing 
. 6          for (Student info: List) {
 7              // determines whether, the found returns 
. 8              IF (info.id == ID)
 . 9                  return index;
 10              // not found on the increment, to find the next 
. 11              index ++ ;
 12 is          }
 13 is          // If all none are found, return -1 
14          return -1;
15     }

Then the next, delete, and modify write is not a difficult thing, and call the method on the line, paste all the code

  . 1  Package org.lanqiao.jwglx;
   2  
  . 3  Import of java.util.ArrayList;
   . 4  Import java.util.List;
   . 5  Import java.util.Scanner;
   . 6  
  . 7  public  class Demo {
   . 8  
  . 9      // by way student class is created inside class 
10      public  static  class Student {
 . 11          // temporarily create three properties, to be understood that the focus is set List 
12 is          public  int ID;
 13 is          public String name;
 14          public String pwd;
 15  
16          //Create a constructor 
. 17          public Student ( int ID, String name, String pwd) {
 18 is              the this .id = ID;
 . 19              the this .name = name;
 20 is              the this .pwd = pwd;
 21 is          }
 22 is  
23 is          // override toString Method 
24          @override
 25          public String toString () {
 26 is              return "Student {" +
 27                      "ID =" + ID +
 28                      ", name = '" + name +' \ '' +
 29                      ", pwd = '"
+ Pwd + '\' +30                      '}' ;
 31          }
 32      }
 33 is  
34 is      // Create a set of global variables List 
35      static List <Student> List = new new the ArrayList <Student> ();
 36      // create input objects 
37 [      static Scanner INPUT = new new Scanner (the System .in);
 38 is  
39      public  static  void main (String [] args) {
 40          // infinite loop so that the menu has been output 
41 is          the while ( to true ) {
 42 is              // print menu 
43             PL ( "------------------------" );
 44              PL ( "1, add student" );
 45              PL ( "2, delete student" );
 46 is              PL ( ". 3, modify student" );
 47              PL ( ". 4, query the student" );
 48              PL ( "0, exit the system" );
 49              PL ( "----------- ------------- " );
 50  
51 is              // function selection 
52 is              Switch (the getInt (" Please enter the number function <0-4>: " )) {
 53 is                  Case . 1 :
54                      // call the Add method to add data 
55                      list.add ( new new64 break ;
65                                                           
                                                           
                                      Case . 4 :
 66                      // use foreach loop through a set of 
67                      for (Student info: List) {
 68                          PL (info.toString ());
 69                      }
 70                      BREAK ;
 71 is                  Case 0 :
 72                      System.exit (0 );
 73 is                  default :
 74                      PL ( "enter the number of bad!" );
 75              }
 76          }
 77      }
 78  
79      // acquired according to the ID set subscript 
80      public  static int getIndexById ( int ID) {
 81          // used to access a variable subscript 
82          int index = 0 ;
 83          // traversing 
84          for (Student info: List) {
 85              // determines whether or not found, returns to find 
86              IF (info.id == ID)
 87                  return index;
 88              // not found on the increment, to find the next 
89              index ++ ;
 90          }
 91 is          // If all none are found, it returns -1 
92          return -1 ;
 93      }
 94  
95     // The following are created as a tool for convenient method, 
96      public  static  void P (String MSG) {
 97          of System.out.print (MSG);
 98      }
 99  
100      public  static  void PL (String MSG) {
 101          the System.out. the println (MSG);
 102      }
 103  
104      public  static  int the getInt (String MSG) {
 105          P (MSG);
 106          return input.nextInt ();
 107      }
 108  
109      public  static String the getString (String MSG) {
 110         p(msg);
111         return input.next();
112     }
113 }

 

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Origin www.cnblogs.com/huajidafahao/p/11295005.html