Sort objects, CompareTo

A first example

Java code

2. /* To compare, let your class implement the comparable interface and rewrite it in the sort order you want CompareTo
4. *map just provides a sort of key, but when we need to sort the values, we provide our own comparators. Here we just modeled the map but didn't actually use the map.
8. */
12. Import Java.util.Iterator;
16. Import Java.util.Set;
18. Import Java.util.TreeSet;
22. Public class Sortbyvalue {
26. public static void Main (string[] args) {
28. set<pair> set = new treeset<pair> ();
30. Set.add (new Pair ("Me", "1000"));
32. Set.add (new Pair ("and", "4000"));
34. Set.add (new Pair ("You", "3000"));
36. Set.add (new Pair ("Food", "10000"));
38. Set.add (new Pair ("Hungry", "5000"));
40. Set.add (new Pair ("later", "6000"));
42. Set.add (new Pair ("Myself", "1000"));
44. For (iterator<pair> i = Set.iterator (); I.hasnext ();)
46. //I like this for statement
48. System.out.println (I.next ());
50. }
52. }
56. Class Pair implements Comparable<object> {
58. Private final String name;
60. private final int number;
64. Public Pair (String name, int number) {
66. this.name = name;
68. this.number = number;
70. }
74. Public Pair (string name, string number) throws NumberFormatException {
76. this.name = name;
78. This.number = integer.parseint (number);
80. }
84. public int compareTo (Object o) {
86. if (o instanceof Pair) {
88. //INT cmp = double.compare (number, (Pair) O). number);
90. INT cmp = number-((Pair) O). number;
92. if (cmp! = 0) {//number is the first to compare, it is equivalent to comparing value first. If the same re-compare key
94. return CMP;
96. }
98. return Name.compareto ((Pair) O). Name);
100. }
102. throw New ClassCastException ("Cannot compare Pair with"
104. + O.getclass (). GetName ());
106. }
110. Public String toString () {
112. return name + ' + number;
114. }
116. }
118. Output Result:
120. Me
122. Myself
124. You
126. and 4000
128. Hungry
130. Later 6000
132. Food 10000

A second example:

Java code

2. Import java.util.*;
6. Public class Namesort {
8. public static void Main (string[] args) {
10. Name[] NameArray = { new Name ("John", "Lennon"),
12. New name ("Karl", "Marx"), new name ("Groucho", "Marx"),
14. New Name ("Oscar", "Grouch")};
16. Arrays.sort (NameArray); Sorts the specified array of objects in ascending order based on the natural ordering of the elements. All elements in an array must implement an Comparable interface. In addition, all meta//elements in the array must be comparable (that is, for any E1 and E2 element in the array, theE1 . CompareTo (E2) shall not throw classcastexception).
18. For (int i = 0; i < namearray.length; i++) {
20. System.out.println (Namearray[i].tostring ());
22. }
24. }
26. }
30. Class Name implements Comparable<name> {
32. Public String FirstName, LastName;
36. Public Name (string firstName, String lastName) {
38. this.firstname = firstName;
40. this.lastname = lastName;
42. }
46. public int compareTo (Name o) { //Implement Interface
48. int lastcmp = Lastname.compareto (o.lastname);
50. //First compare surname (LastName) if last name is the same (lastcmp==0) then compare name (FirstName), otherwise the return name is compared
52. return (lastcmp = = 0 Firstname.compareto (o.firstname): LASTCMP);
54. }
58. Public String toString () { //easy to output test
60. return firstName + "" + lastName;
62. }
64. }
66. Output Result:
68. Oscar Grouch
70. John Lennon
72. Groucho Marx
74. Karl Marx

Java code

2. Look at this beautiful application of the trinocular operator Oh!
4. public int compareTo (Pair o) {
6. int cmp = Number-o.number;
8. return (cmp = = 0 Name.compareto (o.name): CMP);
10. }
12. ----------------------
14. public int compareTo (Name o) { //Implement Interface
16. int lastcmp = Lastname.compareto (o.lastname);
18. //First compare surname (LastName) if last name is the same (lastcmp==0) then compare name (FirstName), otherwise the return name is compared
20. return (lastcmp = = 0 Firstname.compareto (o.firstname): LASTCMP);
    1. }
       
       
       This article reprinted to: http://ocaicai.iteye.com/blog/794438

Sort objects, CompareTo