Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings

Commit f5c5a3d

Browse files
author
Rajeev Kumar Singh
committed
Priority Queue
1 parent 01fdb1f commit f5c5a3d

File tree

3 files changed

+131
-9
lines changed

3 files changed

+131
-9
lines changed
Lines changed: 39 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,39 @@
1+
import java.util.Comparator;
2+
import java.util.PriorityQueue;
3+
4+
public class CreatePriorityQueueExample {
5+
public static void main(String[] args) {
6+
Comparator<String> stringLengthComparator = new Comparator<String>() {
7+
@Override
8+
public int compare(String s1, String s2) {
9+
return s1.length() - s2.length();
10+
}
11+
};
12+
13+
/*
14+
The above Comparator can also be created using lambda expression like this =>
15+
Comparator<String> stringLengthComparator = (s1, s2) -> {
16+
return s1.length() - s2.length();
17+
};
18+
19+
The above statement can be shortened even further like this =>
20+
Comparator<String> stringLengthComparator = Comparator.comparingInt(String::length);
21+
*/
22+
23+
// Create a Priority Queue with a custom Comparator
24+
PriorityQueue<String> namePriorityQueue = new PriorityQueue<>(stringLengthComparator);
25+
26+
// Add items to a Priority Queue (ENQUEUE)
27+
namePriorityQueue.add("Lisa");
28+
namePriorityQueue.add("Robert");
29+
namePriorityQueue.add("John");
30+
namePriorityQueue.add("Chris");
31+
namePriorityQueue.add("Angelina");
32+
namePriorityQueue.add("Joe");
33+
34+
// Remove items from the Priority Queue (DEQUEUE)
35+
while (!namePriorityQueue.isEmpty()) {
36+
System.out.println(namePriorityQueue.remove());
37+
}
38+
}
39+
}
Lines changed: 83 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,83 @@
1+
import java.util.Objects;
2+
import java.util.PriorityQueue;
3+
4+
class Person implements Comparable<Person> {
5+
private String name;
6+
private double salary;
7+
8+
public Person(String name, double salary) {
9+
this.name = name;
10+
this.salary = salary;
11+
}
12+
13+
public String getName() {
14+
return name;
15+
}
16+
17+
public void setName(String name) {
18+
this.name = name;
19+
}
20+
21+
public double getSalary() {
22+
return salary;
23+
}
24+
25+
public void setSalary(double salary) {
26+
this.salary = salary;
27+
}
28+
29+
@Override
30+
public boolean equals(Object o) {
31+
if (this == o) return true;
32+
if (o == null || getClass() != o.getClass()) return false;
33+
Person person = (Person) o;
34+
return Double.compare(person.salary, salary) == 0 &&
35+
Objects.equals(name, person.name);
36+
}
37+
38+
@Override
39+
public int hashCode() {
40+
return Objects.hash(name, salary);
41+
}
42+
43+
@Override
44+
public String toString() {
45+
return "Person{" +
46+
"name='" + name + '\'' +
47+
", salary=" + salary +
48+
'}';
49+
}
50+
51+
// Compare two person objects by their salary
52+
@Override
53+
public int compareTo(Person person) {
54+
if(this.getSalary() > person.getSalary()) {
55+
return 1;
56+
} else if (this.getSalary() < person.getSalary()) {
57+
return -1;
58+
} else {
59+
return 0;
60+
}
61+
}
62+
}
63+
64+
65+
public class PriorityQueueUserDefinedObjectExample {
66+
public static void main(String[] args) {
67+
PriorityQueue<Person> personPriorityQueue = new PriorityQueue<>();
68+
69+
// Add items to the Priority Queue
70+
personPriorityQueue.add(new Person("Rajeev", 100000.00));
71+
personPriorityQueue.add(new Person("Chris", 145000.00));
72+
personPriorityQueue.add(new Person("Andrea", 115000.00));
73+
personPriorityQueue.add(new Person("Jack", 167000.00));
74+
75+
76+
/*
77+
The compare() function implemented in the Person class is used to determine in what order the objects should be dequeued.
78+
*/
79+
while (!personPriorityQueue.isEmpty()) {
80+
System.out.println(personPriorityQueue.remove());
81+
}
82+
}
83+
}

‎java-treeset-examples/src/TreeSetUserDefinedObjectExample.java‎

Lines changed: 9 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -4,19 +4,19 @@
44
import java.util.TreeSet;
55

66
class Employee implements Comparable<Employee> {
7-
private Integer id;
7+
private int id;
88
private String name;
99

10-
public Employee(Integer id, String name) {
10+
public Employee(int id, String name) {
1111
this.id = id;
1212
this.name = name;
1313
}
1414

15-
public Integer getId() {
15+
public int getId() {
1616
return id;
1717
}
1818

19-
public void setId(Integer id) {
19+
public void setId(int id) {
2020
this.id = id;
2121
}
2222

@@ -34,7 +34,7 @@ public boolean equals(Object o) {
3434
if (this == o) return true;
3535
if (o == null || getClass() != o.getClass()) return false;
3636
Employee employee = (Employee) o;
37-
return Objects.equals(id, employee.id);
37+
return id == employee.id;
3838
}
3939

4040
@Override
@@ -45,7 +45,7 @@ public int hashCode() {
4545
// Compare employees based on their IDs
4646
@Override
4747
public int compareTo(Employee employee) {
48-
return this.getId().compareTo(employee.getId());
48+
return this.getId() - employee.getId();
4949
}
5050

5151
@Override
@@ -65,22 +65,22 @@ public static void main(String[] args) {
6565
/*
6666
The requirement for a TreeSet of user defined objects is that
6767
68-
1. Either the object should implement the Comparable interface and provide
68+
1. Either the class should implement the Comparable interface and provide
6969
the implementation for the compareTo() function.
7070
2. Or you should provide a custom Comparator while creating the TreeSet.
7171
*/
7272

7373
SortedSet<Employee> employees = new TreeSet<>();
7474

75-
// TreeSet uses the compareTo() method of the Book class to compare two books and sort them
75+
// TreeSet uses the compareTo() method of the Employee class to compare two employees and sort them
7676
employees.add(new Employee(1010, "Rajeev"));
7777
employees.add(new Employee(1005, "Sachin"));
7878
employees.add(new Employee(1008, "Chris"));
7979

8080
System.out.println("Employees (sorted based on Employee class's compareTo() function)");
8181
System.out.println(employees);
8282

83-
// Using a Custom Comparator
83+
// Providing a Custom Comparator (This comparator compares the employees based on their Name)
8484
employees = new TreeSet<>(Comparator.comparing(Employee::getName));
8585

8686
employees.add(new Employee(1010, "Rajeev"));

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /