The use and traversal of HashMap in Java

the use and traversal of HashMap in JavaCategory: Algorithms and data Structures 2011-10-19 10:53 5345 people read reviews (0) favorite reports Hashmapjavastringobjectiteratorlist

1: A simple example of using HashMap

[Java]View Plaincopy

2. Package com.pb.collection;
6. Import Java.util.HashMap;
8. Import Java.util.Iterator;
10. Import Java.util.Set;
12. Import Java.util.Map.Entry;
16. Public class Hashmapdemo {
20. public static void Main (string[] args) {
24. hashmap<string, string> HashMap = new hashmap<string, string> ();
26. Hashmap.put ("cn", "China");
28. Hashmap.put ("JP", "Japan");
30. Hashmap.put ("fr", "France");
34. System.out.println (HASHMAP);
36. System.out.println ("cn:" + hashmap.get ("cn"));
38. System.out.println (Hashmap.containskey ("cn"));
40. System.out.println (Hashmap.keyset ());
42. System.out.println (Hashmap.isempty ());
46. Hashmap.remove ("cn");
48. System.out.println (Hashmap.containskey ("cn"));
52. //Using iterator traversal HashMap
54. Iterator it = Hashmap.keyset (). Iterator ();
56. While (It.hasnext ()) {
58. String key = (string) it.next ();
60. System.out.println ("key:" + key);
62. System.out.println ("value:" + hashmap.get (key));
64. }
68. //Another way to traverse HashMap
70. set<entry<string, string>> sets = Hashmap.entryset ();
72. for (entry<string, string> entry:sets) {
74. System.out.print (Entry.getkey () + ",");
76. System.out.println (Entry.getvalue ());
78. }
80. }
82. }

2: An example of a combination of list and HASHMAP implementations

[Java]View Plaincopy

2. Import Java.util.Iterator;
4. Import java.util.List;
6. Import Java.util.HashMap;
8. Import java.util.ArrayList;
10. Import Java.util.Map;
12. Import Java.util.Scanner;
14. Import Java.util.Set;
16. Import Java.util.Map.Entry;
18. /**
20. * In the case of not creating student classes, enter n student information from the keyboard (school number, name, age),
22. * When the input is complete, print out the individual student information
24. * @author Ccna_zhang
26. *
28. */
30. Public class Assignment {
34. public static void Main (string[] args) {
38. //Define a list that holds student information, with an element type of HashMap
40. listnew arraylist
42. Scanner input = new Scanner (system.in);
46. System.out.println ("Please enter the student's information, y means continue, n means exit");
48. While ("Y". Equals (Input.next ())) {
50. hashmap<string, object> map = new hashmap<string, object> ();
52. System.out.println ("Please enter the study number");
54. Map.put ("Studentno", Input.next ());
56. System.out.println ("Please enter name");
58. Map.put ("name", Input.next ());
60. System.out.println ("Please enter Age");
62. Map.put ("Age", Input.nextint ());
64. List.add (map);
66. System.out.println ("Please continue to enter the student's information, y means continue, n means exit");
68. }
72. System.out.println ("The Student information entered is:");
74. System.out.println ("Number of Students:" + list.size ());
78. Iterator
80. int i = 1;
82. While (It.hasnext ()) {
84. hashmap<string, object> stumap = It.next ();
86. System.out.print ("First" + i + "student's Information");
88. System.out.println ("School Number:" + stumap.get ("Studentno") + ", Name:" + stumap.get ("name") + ", Age:" + STUMAP.G  ET ("age"));
90. }
92. }
94. }

Usage and traversal of HashMap in Java (RPM)