Java LinkedHashMap example code - Put, Get, Remove and Clear

How do you store an object in a LinkedHashMap and access it ?

In this example we store an employee information into a LinkedHashMap with the employee number as the key. We learn the following in this tutorial
  • How to save data into a HashMap
  • Read all data from the HashMap
  • Read a specific entry from the map by key value
  • Delete an entry from the map
  • Remove all saved entries from the map

Sample source code for Employee Java Bean
?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
package com.as400samplecode;
 
public class Employee {
 
 int employeeNumber;
 String employeeName;
 String employeePosition;
 Double employeeSalary;
 
 public int getEmployeeNumber() {
  return employeeNumber;
 }
 public void setEmployeeNumber(int employeeNumber) {
  this.employeeNumber = employeeNumber;
 }
 public String getEmployeeName() {
  return employeeName;
 }
 public void setEmployeeName(String employeeName) {
  this.employeeName = employeeName;
 }
 public String getEmployeePosition() {
  return employeePosition;
 }
 public void setEmployeePosition(String employeePosition) {
  this.employeePosition = employeePosition;
 }
 public Double getEmployeeSalary() {
  return employeeSalary;
 }
 public void setEmployeeSalary(Double employeeSalary) {
  this.employeeSalary = employeeSalary;
 }
 
 
}

Sample java source code for LinkedHashMap
?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
package com.as400samplecode;
 
import java.util.Iterator;
import java.util.LinkedHashMap;
 
public class MyHashMap {
 
 public static void main(String[] args)
 {
  //Create Hash Map of Field Definitions
  LinkedHashMap hashMap = new LinkedHashMap(4);
 
  //Store data
  Employee employeeInfo = new Employee();
 
  employeeInfo.setEmployeeNumber(111);
  employeeInfo.setEmployeeName("John");
  employeeInfo.setEmployeePosition("Programmer");
  employeeInfo.setEmployeeSalary(10000.01);
  hashMap.put(111, employeeInfo);
 
  employeeInfo = new Employee();
  employeeInfo.setEmployeeNumber(112);
  employeeInfo.setEmployeeName("Albert");
  employeeInfo.setEmployeePosition("Programmer");
  employeeInfo.setEmployeeSalary(10000.02);
  hashMap.put(112, employeeInfo);
 
  employeeInfo = new Employee();
  employeeInfo.setEmployeeNumber(113);
  employeeInfo.setEmployeeName("Gary");
  employeeInfo.setEmployeePosition("Programmer");
  employeeInfo.setEmployeeSalary(10000.03);
  hashMap.put(113, employeeInfo);
 
  employeeInfo = new Employee();
  employeeInfo.setEmployeeNumber(114);
  employeeInfo.setEmployeeName("Bob");
  employeeInfo.setEmployeePosition("Manager");
  employeeInfo.setEmployeeSalary(10000.04);
  hashMap.put(114, employeeInfo);
 
 
  //Read the whole HashMap
  Iterator iterator = hashMap.keySet().iterator();
  while (iterator.hasNext()) {
   Integer key = (Integer) iterator.next();
   employeeInfo = hashMap.get(key);
   System.out.println("--->");
   System.out.println(employeeInfo.getEmployeeNumber());
   System.out.println(employeeInfo.getEmployeeName());
   System.out.println(employeeInfo.getEmployeePosition());
   System.out.println(employeeInfo.getEmployeeSalary());
  }
 
  // Output
  // --->
  // 111
  // John
  // Programmer
  // 10000.01
  // --->
  // 112
  // Albert
  // Programmer
  // 10000.02
  // --->
  // 113
  // Gary
  // Programmer
  // 10000.03
  // --->
  // 114
  // Bob
  // Manager
  // 10000.04
 
 
  //Read a specific entry
  employeeInfo = hashMap.get(113);
  System.out.println("--->");
  System.out.println(employeeInfo.getEmployeeNumber());
  System.out.println(employeeInfo.getEmployeeName());
  System.out.println(employeeInfo.getEmployeePosition());
  System.out.println(employeeInfo.getEmployeeSalary());
 
  // Output
  // --->
  // 113
  // Gary
  // Programmer
  // 10000.03
 
 
  //Remove an entry
  employeeInfo = hashMap.remove(112);
  //Read the whole HashMap
  iterator = hashMap.keySet().iterator();
  while (iterator.hasNext()) {
   Integer key = (Integer) iterator.next();
   employeeInfo = hashMap.get(key);
   System.out.println("--->");
   System.out.println(employeeInfo.getEmployeeNumber());
   System.out.println(employeeInfo.getEmployeeName());
   System.out.println(employeeInfo.getEmployeePosition());
   System.out.println(employeeInfo.getEmployeeSalary());
  }
 
  // Output
  // --->
  // --->
  // 111
  // John
  // Programmer
  // 10000.01
  // --->
  // 113
  // Gary
  // Programmer
  // 10000.03
  // --->
  // 114
  // Bob
  // Manager
  // 10000.04
 
 
  //Clear all the entries
  hashMap.clear();
  System.out.println("Total key value pairs in LinkedHashMap are : " + hashMap.size());
 
  // Output
  // Total key value pairs in LinkedHashMap are : 0
 
 }
 
}
Labels:

No comments:

Post a Comment

NO JUNK, Please try to keep this clean and related to the topic at hand.
Comments are for users to ask questions, collaborate or improve on existing.