LAB Activity 02182026
2026-02-18 17:03
Tags: #java
Author: Duke Hsu
Types of Functions
- Method with No parameters & No return values
- Method with parameters & No return values
- Method with return values & No parameters
- Method with return values & parameters
Concepts
-
parameters
Use parameters when you define a method.
-
arguments
Use arguments when your object calls a method with parameters.
Get the argument from input or return it.
-
return
The return value is not the same as printing out results.
When you want the return values to be printed out, you should assign a variable to this object's methods.
-
constructor
When you create a new object, the class method will construct it.
-
object
An object is an entity.
-
instantiate
To instantiate means to create a new object.
-
rename class (refactor)
Use refactoring to rename the class.
-
scanner
A scanner accepts user input in the form of text, integers, or data.
Syntax
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 | accessModifier class className{
//attributes
//if no accessModifier , ther defualt is public
accessModifier data_type attributesName = attributesValues;
//methods no return
accessModifier void methodName(){
//method block
System.our.println("Hello World");
}
//method with parameter and return
accessModifier String methodName(int studID, String studName, dataType attributes){
//assign parameter values to class attributes
studentID = studID;
studentName = studName;
class_attributes = method_parameters;
//method block
System.our.println("Hello World");
return "The values " +studentID+ "."
}
}
|
Code block
Method with No parameters & No return values
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 | /*
* Click
nbfs://nbhost/SystemFileSystem/Templates/Licenses/license-default.txt to
change this license
* Click nbfs://nbhost/SystemFileSystem/Templates/Classes/Main.java to edit
this template
*/
package prjmyfirstclass;
/**
*
* @author student
*/
public class PrjMyFristSampleClass {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
//instantiate the object
Student athlete = new Student(); //student() is the constructor
//send a message to call displayInformation() - object.method -call method
athlete.displayInformation();
}//end of main method
}//end of main class
//class Student for object later - blue print //class Student for object later - blue print
class Student{
//attributes accessModifier - dataType - attributesName ;
//use accessmodifier protected the attributes
private int studentID = 0;
private String studentName = "";
private String studentCourse = "";
//methods no parameter and no return - no need attributes from other method
public void displayInformation(){
//assign values
//method local attributes
studentID = 20251234;
studentName = "YongLou, Xu";
studentCourse = "BSIT";
//condition - compare dealer variable or class attributes
if(studentID == 20251234){
//print out - new line
System.out.println("The student enrolled is: "+
studentName + ", with the student number: "+
studentID + " and course: "+
studentCourse + "."); //from student class attributes
}//end of if
else{
System.out.println("No enrolled student with student number: "
+ studentID);
}//end of else
}//end of displayInformation method with out parameter and no return value
}
|
Method with parameters & No return values
main method
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21 | //main method
public class PrjMyFristSampleClass {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
//instantiate the object
Student athlete = new Student(); //student() is the constructor
//send a message to call displayInformation() - object.method -
call method
//athlete.displayInformation();
//call method with arguments
athlete.displayInformation(202215568, "YongLou, Xu", "BSIT");
}//end of main method
}//end of main class
|
displayInfomation method
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 | //over loading
//methods with parameter and no return
public void displayInformation(int studID, String studName, String
studCourse){
//assign parameter values to class attributes
studentID = studID;
studentName = studName;
studentCourse = studCourse;
//condition - compare dealer variable or class attributes
if(studentID == 202215568){
//print out - new line
System.out.println("The student enrolled is: "+
studentName + ", with the student number: "+
studentID + " and course: "+studentCourse + "."); //from student class
attributes
}//end of if
else{
System.out.println("No enrolled student with student number: "
+ studentID);
}//end of else
}//end of displayInformation(parameter) method with parameter and noreturn value
}
|
Method with return values & No parameters
main method
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17 | public class PrjMyFristSampleClass {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
//instantiate the object
Student athlete = new Student(); //student() is the constructor
/*call have return value method
store return values and received it to message variable*/
String messages = athlete.enroll();
System.out.println(messages);
}//end of main method
}//end of main class
|
enrollmethod
1
2
3
4
5
6
7
8
9
10
11
12
13
14 | //need return , so the method data type is String
public String enroll(){
//assign values to class attributes
studentID = 202215568;
studentName = "YongLou,Xu";
studentCourse = "BSIT";
//return message
return "The student: "+ studentName +
" with student name: " + studentID +
" and course: " + studentCourse +
" was enrolled.";
}//end of enroll method - with return values
|
Method with return values & parameters
mainmethod
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 | //don't forget import the package
import java.util.Scanner;
public class PrjMyFristSampleClass {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
//instantiate the object
Student athlete = new Student(); //student() is the constructor
/*ask user inputs for student ID, name and courses*/
int studID = 0;
String studName="";
String studCourse="";
//scanner class//instantiate a Scanner object for user input
Scanner input = new Scanner(System.in);
//reminder user input
System.out.print("Enter your student ID: ");
studID = input.nextInt();
//next line
input.nextLine();
//name input
System.out.print("Enter your student Name: ");
studName = input.nextLine();
// course input
System.out.print("Enter your Course: ");
studCourse = input.nextLine();
//send message to call the enroll() with passed argument for the
parameter
String message = athlete.enroll(studID, studName, studCourse);
System.out.println(message);
}//end of main method
}//end of main class
|
enrollmethod
1
2
3
4
5
6
7
8
9
10
11
12
13
14 | //method with parameter and return values
public String enroll(int studID, String studName, String studCourse){
//assign parameter values to class attributes
studentID = studID;
studentName = studName;
studentCourse = studCourse;
//return message
return "The student: "+ studentName +
" with student name: " + studentID +
" and course: " + studentCourse +
" was enrolled.";
}
|
References
Instructor’s In-Class Demonstration
OOP - Module 2. Object Oriented Programming Fundamentals part 2.pptx