comparator sort and order java

comparesortandorder.java

 1 /*
 2  * To change this template, choose Tools | Templates
 3  * and open the template in the editor.
 4  */
 5 package checkex;
 6 
 7 import java.text.DateFormat;
 8 import java.text.ParseException;
 9 import java.text.SimpleDateFormat;
10 import java.util.ArrayList;
11 import java.util.Collections;
12 import java.util.Comparator;
13 import java.util.Date;
14 import java.util.List;
15 import java.util.logging.Level;
16 import java.util.logging.Logger;
17 
18 /**
19  *
20  * @author 
21  */
22 public class comparesortandorder {
23     public static void main(String[] args) {
24         List<Person> persons = new java.util.ArrayList<Person>();
25         persons.add(new Person("a", "def5", -10, "10/10/12"));
26         persons.add(new Person("a", "def3", 70, "01/01/13"));
27         persons.add(new Person("b", "def22", 32, "01/01/2013"));
28         persons.add(new Person("b", "def1", 65, "01/01/13"));
29         persons.add(new Person("a", "def4", -10, "10/10/12"));
30         persons.add(new Person("a", "def4", -10, "10/10/19"));
31         persons.add(new Person("c", "def22", 10, "01/01/2013"));
32         persons.add(new Person("c", "def21", 10, "01/01/2013"));
33         
34         System.out.println(persons);
35         Collections.sort(persons, new Comparator<Person>() {
36 
37             @Override
38             public int compare(Person t, Person t1) {
39                 //return t.getAge() - t1.getAge();
40                         if(0 == t.getAge() || 0== t1.getAge() ){
41             throw new NullPointerException();
42         }else{
43             int nameComparisonResult = t.getAge()-(t1.getAge());
44             if(0 == nameComparisonResult){
45                 return t.getLname().compareTo(t1.getLname());
46             }else{
47                 return nameComparisonResult;
48             }
49         }
50             }
51         });
52         System.out.println(persons);
53         
54         
55         List<Person> a1 = new ArrayList<Person>();
56         for (int i = 0; i < persons.size(); i++) {
57                         if((persons.get(i).getFname() == "a") || (persons.get(i).getFname() == "d") ){
58                             a1.add(new Person(persons.get(i).getFname(), persons.get(i).getLname(),persons.get(i).getAge(), persons.get(i).getDateval()));
59                         }
60                 }
61         System.out.println(a1);
62         
63         Collections.sort(a1, new Comparator<Person>() {
64 
65             @Override
66             public int compare(Person o1, Person o2) {
67                  //To change body of generated methods, choose Tools | Templates.
68 
69            if (o1.getDateval() == null || o2.getDateval() == null)
70         return 0;
71                 try {
72                     return converttodate(o1.getDateval()).compareTo(converttodate(o2.getDateval()));
73                 } catch (ParseException ex) {
74                     Logger.getLogger(comparesortandorder.class.getName()).log(Level.SEVERE, null, ex);
75                 }
76                 return 0;
77             }
78         
79         });
80         System.out.println(a1);
81         
82 
83     }
84     public static Date converttodate(String dateval) throws ParseException {
85        
86 DateFormat formatter ; 
87 Date date ; 
88    formatter = new SimpleDateFormat("MM/dd/yy");
89    date = formatter.parse(dateval);
90         return date;
91         
92         
93     }
94 }
95 

Person.java

 1 /*
 2  * To change this template, choose Tools | Templates
 3  * and open the template in the editor.
 4  */
 5 package checkex;
 6 
 7 /**
 8  *
 9  * @author 
10  */
11 public class Person {
12     String fname;
13     String lname;
14     String dateval;
15     int age;
16 
17     public Person() {
18     }
19 
20     public int getAge() {
21         return age;
22     }
23 
24     public void setAge(int age) {
25         this.age = age;
26     }
27     public String getDateval() {
28         return dateval;
29     }
30 
31     public void setDateval(String dateval) {
32         this.dateval = dateval;
33     }
34 
35     public String getFname() {
36         return fname;
37     }
38 
39     public void setFname(String fname) {
40         this.fname = fname;
41     }
42 
43     public String getLname() {
44         return lname;
45     }
46 
47     public void setLname(String lname) {
48         this.lname = lname;
49     }
50 
51     public Person(String fname, String lname, int age, String dateval) {
52         this.fname = fname;
53         this.lname = lname;
54         this.age = age;
55         this.dateval = dateval;
56     }
57 
58     @Override
59     public String toString() {
60         return fname + "," + lname + "," + age+","+dateval;
61     }
62 }
63