General object sorting based on Java reflection

/**
* @ Title: objectsort. Java
* @ Package sort
* @ Description: Todo (describe the file in one sentence)
* @ Author youjianbo
* @ Date 2011-3-9 10:28:53 AM
* @ Version V1.0
*/
Package sort;

Import java. Lang. Reflect. method;
Import java. Math. bigdecimal;
Import java. Text. collationkey;
Import java. Text. collator;
Import java. util. arraylist;
Import java. util. collections;
Import java. util. comparator;
Import java. util. List;

Public class objectsort {

/**
* @ Param ARGs
*/
Public static void main (string [] ARGs ){
/**
*
* Author: youjianbo
* Date: 2008-6-27
* Purpose: sorts objects by one or more attributes.
* Java contains eight basic data types: Boolean, byte, Char, short, Int, float, douboe, and long.
* Only non-Boolean and byte attributes are compared, which are applicable to most application environments. If you have special requirements, modify them by yourself.
* You only need to pass in the object attribute list and list to be sorted.
***/
List arraydemo = new arraylist ();

Person p1 = new person ();
P1.setname ("James ");
P1.setage (200 );
P1.setsalary (100 );

Person P2 = new person ();
P2.setname ("Li Si ");
P2.setage (22 );
P2.setsalary (100 );

Person P3 = new person ();
P3.setname ("Wang Wu ");
P3.setage (25 );
P3.setsalary (1900 );

Person P4 = new person ();
P4.setname ("Zhao six ");
P4.setage (25 );
P4.setsalary (3000 );

Person P5 = new person ();
P5.setname ("Liu Qi ");
P5.setage (30 );
P5.setsalary (2000 );

Person P6 = new person ();
P6.setname ("Luba ");
P6.setage (25 );
P6.setsalary (2000 );

Person P7 = new person ();
P7.setname (" 9 ");
P7.setage (26 );
P7.setsalary (2000 );

Person P8 = new person ();
P8.setname (" ");
P8.setage (22 );
P8.setsalary (2000 );

Arraydemo. Add (P1 );
Arraydemo. Add (P2 );
Arraydemo. Add (P3 );
Arraydemo. Add (P4 );
Arraydemo. Add (P5 );
Arraydemo. Add (P6 );
Arraydemo. Add (P7 );
Arraydemo. Add (P8 );

// ********** Start to compare ********//
Commoncomparator comparator = new commoncomparator ();

// System. Out. println ("------ 0. Compare ---------" by name ---------");
// Comparator. setfields_user (New String [] {"name "});
// Collections. Sort (arraydemo, comparator );
// For (INT I = 0; I <arraydemo. Size (); I ++)
//{
// Person = (person) arraydemo. Get (I );
// System. out. println ("username:" + person. getname () + "Age:" + person. getage () + "monthly salary:" + person. getsalary ());
//}
// System. Out. println ("------ 1. Compare ---------" by age ---------");
// Comparator. setfields_user (New String [] {"Age "});
// Collections. Sort (arraydemo, comparator );
// For (INT I = 0; I <arraydemo. Size (); I ++)
//{
// Person = (person) arraydemo. Get (I );
// System. out. println ("username:" + person. getname () + "Age:" + person. getage () + "monthly salary:" + person. getsalary ());
//}
//
// System. Out. println ("------ 1. Compare the monthly salary from low to high ---------");
// Comparator. setfields_user (New String [] {"salary "});
// Collections. Sort (arraydemo, comparator );
// For (INT I = 0; I <arraydemo. Size (); I ++)
//{
// Person = (person) arraydemo. Get (I );
// System. out. println ("username:" + person. getname () + "Age:" + person. getage () + "monthly salary:" + person. getsalary ());
//}

// System. Out. println ("------ 1. Comparison of age and monthly salary ---------");
// Comparator. setfields_user (New String [] {"Age", "salary "});
// Collections. Sort (arraydemo, comparator );
// For (INT I = 0; I <arraydemo. Size (); I ++)
//{
// Person = (person) arraydemo. Get (I );
// System. out. println ("username:" + person. getname () + "Age:" + person. getage () + "monthly salary:" + person. getsalary ());
//}
//
// System. Out. println ("------ 1. Compare the monthly salary and age ---------");
// Comparator. setfields_user (New String [] {"salary", "Age "});
// Collections. Sort (arraydemo, comparator );
// For (INT I = 0; I <arraydemo. Size (); I ++)
//{
// Person = (person) arraydemo. Get (I );
// System. out. println ("username:" + person. getname () + "Age:" + person. getage () + "monthly salary:" + person. getsalary ());
//}
System. Out. println ("------ 1. Compare the age and monthly salary by name ---------");
Comparator. setfields_user (New String [] {"name", "Age", "salary "});
Collections. Sort (arraydemo, comparator );
For (INT I = 0; I <arraydemo. Size (); I ++)
{
Person = (person) arraydemo. Get (I );
System. out. println ("username:" + person. getname () + "--- age:" + person. getage () + "---- monthly salary:" + person. getsalary ());
}

System. Out. println ("------ 1. Compare monthly salary and age ---------");
Comparator. setfields_user (New String [] {"salary", "Age "});
Collections. Sort (arraydemo, comparator );
For (INT I = 0; I <arraydemo. Size (); I ++)
{
Person = (person) arraydemo. Get (I );
System. Out. println ("username:" + person. getname () + "Age:" + person. getage () + "monthly salary:" + person. getsalary ());
}
}

}

Class commoncomparator implements Comparator
{
/***
* @ Param
* The property of the comparison object is passed in the form of string [].
* The comparison object must comply with the JavaBean, that is, the set and get methods must be available.
**/
String [] fields_user = NULL;


Public String [] getfields_user (){
Return fields_user;
}
Public void setfields_user (string [] fields_user ){
This. fields_user = fields_user;
}
/**
* Define sorting rules
* Sort by more than one attribute
* This sorting is performed according to the order of attributes. The class is SQL order.
* That is, if the attribute at the same position is compared, it is stopped.
**/
Public int compare (Object obj1, object obj2)
{
// If no attribute exists, it is not sorted.
If (fields_user = NULL | fields_user.length <= 0)
{
Return 2; // do not compare
}
For (INT I = 0; I <fields_user.length; I ++)
{
Return comparefield (obj1, obj2, fields_user [I]);
}
Return 0;
}
/**
* @ Param fieldname
* Sort by attribute name
**/
Private Static int comparefield (Object O1, object O2, string fieldname)
{
Try
{
Object value1 = getfieldvaluebyname (fieldname, O1 );
Object value2 = getfieldvaluebyname (fieldname, O2 );

// -- String comparison
If (value1 instanceof string)
{
String V1 = getfieldvaluebyname (fieldname, O1). tostring ();
String v2 = getfieldvaluebyname (fieldname, O2). tostring ();
Collator mycollator = collator. getinstance ();
Collationkey [] keys = new collationkey [5];
Keys [0] = mycollator. getcollationkey (V1 );
Keys [1] = mycollator. getcollationkey (V2 );
Return (Keys [0]. compareto (Keys [1]);
// ------- Chinese characters may be faulty --------
// String V1 = getfieldvaluebyname (fieldname, O1). tostring ();
// String v2 = getfieldvaluebyname (fieldname, O2). tostring ();
//
// If (v1.compareto (V2)> 0 ){
// Return 1;
//} Else if (v1.compareto (V2) = 0 ){
// Return 0;
//} Else {
// Return-1;
//}
}
// -- Non-Comparative attributes are not compared
Else if ("Java. lang. boolean ". equals (value1.getclass (). getname () | "Java. lang. byte ". equals (value1.getclass (). getname ()))
{
Return 0;
} Else
{
Bigdecimal b1 = new bigdecimal (value1.tostring ());
Bigdecimal b2 = new bigdecimal (value2.tostring ());
Return b1.compareto (B2 );
}

} Catch (exception E)
{
System. Out. println ("-----------------------------------------------------------------------------");
System. Out. println ("--------- this attribute of the object does not exist or cannot be reflected on this security level. For details, see Java Doc --------");
System. Out. println ("-----------------------------------------------------------------------------");
E. printstacktrace ();
}
// Less
Return-1;
}
/**
* @ Param
* Fieldname attribute name
* OBJ object
* Obtain the attribute value through reflection.
**/
Private Static object getfieldvaluebyname (string fieldname, object OBJ)
{
Try
{
String letter = fieldname. substring (0, 1). touppercase ();
String methodstr = "get" + letter + fieldname. substring (1 );
Method method = obj. getclass (). getmethod (methodstr, new class [] {});

Object value = method. Invoke (OBJ, new object [] {});

Return value;
} Catch (exception E)
{
System. Out. println ("------------------------------------------------------");
System. Out. println ("--------- this" + fieldname + "property does not exist ----------------------");
System. Out. println ("------------------------------------------------------");
Return NULL;
}
}
}

Class person
{
Public Person (){}

Private string name;
Private int age;
Private long salary;

Public long getsalary (){
Return salary;
}
Public void setsalary (long salary ){
This. Salary = salary;
}
Public int getage (){
Return age;
}
Public void setage (INT age ){
This. Age = age;
}
Public String getname (){
Return name;
}
Public void setname (string name ){
This. Name = Name;
}
}