package com.company;
import java.util.Scanner;
// i wish i can use enum :(, sadly i do not know how to implement it in java.
class studentInformation
{
//attributes
private int studentID;
private String firstName;
private String lastName;
private String middleName;
private String department;
//function that returns details of student information
public void printAllinfo()
{
System.out.println(studentID);
System.out.println(firstName);
System.out.println(lastName);
System.out.println(middleName);
System.out.println(department);
System.out.println();
}
public int getstudentID()
{
return studentID;
}
public String getfirstname()
{
return firstName;
}
public String getmiddlename()
{
return middleName;
}
public String getLastname()
{
return lastName;
}
public String getdepartment()
{
return department;
}
public void setAllinfoatOnce(int studentID, String firstName, String middleName, String lastName, String department)
{
this.studentID = studentID;
this.firstName = firstName;
this.middleName = middleName;
this.lastName = lastName;
this.department = department;
}
public void setStudentID(int studentID)
{
this.studentID = studentID;
}
public void setFirstName(String firstName)
{
this.firstName = firstName;
}
public void setLastName(String lastName)
{
this.lastName = lastName;
}
public void setMiddleName(String middleName)
{
this.middleName = middleName;
}
public void setDepartment(String department)
{
this.department = department;
}
//constructor
public studentInformation(int studentID, String firstName, String middleName, String lastName, String department)
{
this.studentID = studentID;
this.firstName = firstName;
this.middleName = middleName;
this.lastName = lastName;
this.department = department;
}
public studentInformation()
{
//default constructor
}
}
public class Main
{
public static void main(String[] args)
{
int objectcounter =0;
int objectfilled[] ;
int menu =0;
Scanner inputmain = new Scanner(System.in);
String temp;
String choice ="Yes";
objectfilled = new int[20];
for(int i =0;i<20;i++)
{
objectfilled[i]=0;
//System.out.println(objectfilled[i]);
}
studentInformation [] studentarray;
studentarray = new studentInformation[20];// instantiate 20 objects
studentarray[objectcounter] = new studentInformation(1,"Hanrickson","Etrone","Dumapit","Institute of computer studies");
objectfilled[objectcounter] =1;
objectcounter++;
studentarray[objectcounter]= new studentInformation(2,"Wisn","Derpe","Grandtesorro","Engineering department");
objectfilled[objectcounter] =1;
for (int i =2;i<20;i++)
{
studentarray[i] = new studentInformation();
}
objectcounter++;
boolean loop = true;
while (loop)
{
if(menu!=-1)
{
System.out.println("");
System.out.println("To display all student information enter 1.");
System.out.println("To continue adding student information enter 2.");
System.out.println("To modify the student information enter 3.");
System.out.println("To delete the information 4.");
System.out.println("To exit application enter 5.");
}
System.out.print("Enter choice: ");
// input choice
temp = inputmain.next();
//error handling
if(temp.length()<=1 && ((temp.charAt(0)>=49) && (temp.charAt(0) <= 57)))
{
menu = Integer.parseInt(temp)-1;
//System.out.print(menu);
}
else
{
menu =-1;
}
switch (menu)
{
//display, BECAUSE I DO NOT KNOW HOW TO INTEGRATE THE ENUM USING JAVA, only in cpp :(
case 0:
{
System.out.println("No. ID no. Firstname Middlename Lastname Department");
for (int i =0; i<20;i++)
{
if(objectfilled[i] ==1)
{
System.out.print(i+1);
System.out.print(" ");
System.out.print(studentarray[i].getstudentID());
System.out.print(" ");
System.out.print(studentarray[i].getfirstname());
System.out.print(" ");
System.out.print(studentarray[i].getmiddlename());
System.out.print(" ");
System.out.print(studentarray[i].getLastname());
System.out.print(" ");
System.out.print(studentarray[i].getdepartment());
System.out.println(" ");
}
}
break;
}
case 1:// add student information
{
//find available slot
for (int i= 0;i<20;i++)
{
if(objectfilled[i] == 0)
{
//input slot
//2studentarray[i]
System.out.print("Enter Student ID: ");
studentarray[i].setStudentID(inputmain.nextInt());
System.out.print("Enter Firstname: ");
studentarray[i].setFirstName(inputmain.next());
System.out.print("Enter Middlename: ");
studentarray[i].setMiddleName(inputmain.next());
System.out.print("Enter Lastname: ");
studentarray[i].setLastName(inputmain.next());
System.out.print("Enter Department: ");
studentarray[i].setDepartment(inputmain.next());
objectfilled[i] =1;
objectcounter++;
break;
}
}
System.out.println("Information added");
System.out.println();
break;
}
case 2: // modify
{
System.out.println("No. ID no. Firstname Middlename Lastname Department");
for (int i =0; i<20;i++)
{
if(objectfilled[i] ==1)
{
System.out.print(i+1);
System.out.print(" ");
System.out.print(studentarray[i].getstudentID());
System.out.print(" ");
System.out.print(studentarray[i].getfirstname());
System.out.print(" ");
System.out.print(studentarray[i].getmiddlename());
System.out.print(" ");
System.out.print(studentarray[i].getLastname());
System.out.print(" ");
System.out.print(studentarray[i].getdepartment());
System.out.println(" ");
}
}
// ask to what to modify
boolean inputdone = true;
while (inputdone)
{
System.out.print("Enter no. to modify : ");
temp = inputmain.next();
//error handling
if (temp.length() <= 2)
{
int numbertodelete = Integer.parseInt(temp)-1;
//System.out.println(numbertodelete);
System.out.print("Enter Student ID: ");
studentarray[numbertodelete].setStudentID(inputmain.nextInt());
System.out.print("Enter Firstname: ");
studentarray[numbertodelete].setFirstName(inputmain.next());
System.out.print("Enter Middlename: ");
studentarray[numbertodelete].setMiddleName(inputmain.next());
System.out.print("Enter Lastname: ");
studentarray[numbertodelete].setLastName(inputmain.next());
System.out.print("Enter Department: ");
studentarray[numbertodelete].setDepartment(inputmain.next());
//System.out.println(objectcounter);
System.out.println("Modified");
inputdone = false;
}
}
break;
}
case 3: // delete
{
//display information
System.out.println("No. ID no. Firstname Middlename Lastname Department");
for (int i =0; i<20;i++)
{
if(objectfilled[i] ==1)
{
System.out.print(i+1);
System.out.print(" ");
System.out.print(studentarray[i].getstudentID());
System.out.print(" ");
System.out.print(studentarray[i].getfirstname());
System.out.print(" ");
System.out.print(studentarray[i].getmiddlename());
System.out.print(" ");
System.out.print(studentarray[i].getLastname());
System.out.print(" ");
System.out.print(studentarray[i].getdepartment());
System.out.println(" ");
}
}
// ask to what to modify
boolean inputdone = true;
while (inputdone)
{
System.out.print("Enter no. to delete : ");
temp = inputmain.next();
//error handling
if (temp.length() <= 2)
{
int numbertodelete = Integer.parseInt(temp)-1;
//System.out.println(numbertodelete);
objectfilled[numbertodelete] =0;
studentarray[numbertodelete].setStudentID(0);
studentarray[numbertodelete].setFirstName("");
studentarray[numbertodelete].setMiddleName("");
studentarray[numbertodelete].setLastName("");
studentarray[numbertodelete].setDepartment("");
//System.out.println(objectcounter);
System.out.println("deleted");
inputdone = false;
}
}
break;
}
case 4:
{
// terminate application
loop = false;
break;
}
default:
{
break;
}
}
}
inputmain.close();
}
}
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OneCompiler's Java online editor supports stdin and users can give inputs to the programs using the STDIN textbox under the I/O tab. Using Scanner class in Java program, you can read the inputs. Following is a sample program that shows reading STDIN ( A string in this case ).
import java.util.Scanner;
class Input {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter your name: ");
String inp = input.next();
System.out.println("Hello, " + inp);
}
}
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apply plugin:'application'
mainClassName = 'HelloWorld'
run { standardInput = System.in }
sourceSets { main { java { srcDir './' } } }
repositories {
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dependencies {
// add dependencies here as below
implementation group: 'org.apache.commons', name: 'commons-lang3', version: '3.9'
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Java is a very popular general-purpose programming language, it is class-based and object-oriented. Java was developed by James Gosling at Sun Microsystems ( later acquired by Oracle) the initial release of Java was in 1995. Java 17 is the latest long-term supported version (LTS). As of today, Java is the world's number one server programming language with a 12 million developer community, 5 million students studying worldwide and it's #1 choice for the cloud development.
short x = 999; // -32768 to 32767
int x = 99999; // -2147483648 to 2147483647
long x = 99999999999L; // -9223372036854775808 to 9223372036854775807
float x = 1.2;
double x = 99.99d;
byte x = 99; // -128 to 127
char x = 'A';
boolean x = true;
When ever you want to perform a set of operations based on a condition If-Else is used.
if(conditional-expression) {
// code
} else {
// code
}
Example:
int i = 10;
if(i % 2 == 0) {
System.out.println("i is even number");
} else {
System.out.println("i is odd number");
}
Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.
switch(<conditional-expression>) {
case value1:
// code
break; // optional
case value2:
// code
break; // optional
...
default:
//code to be executed when all the above cases are not matched;
}
For loop is used to iterate a set of statements based on a condition. Usually for loop is preferred when number of iterations is known in advance.
for(Initialization; Condition; Increment/decrement){
//code
}
While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.
while(<condition>){
// code
}
Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.
do {
// code
} while (<condition>);
Class is the blueprint of an object, which is also referred as user-defined data type with variables and functions. Object is a basic unit in OOP, and is an instance of the class.
class keyword is required to create a class.
class Mobile {
public: // access specifier which specifies that accessibility of class members
string name; // string variable (attribute)
int price; // int variable (attribute)
};
Mobile m1 = new Mobile();
public class Greeting {
static void hello() {
System.out.println("Hello.. Happy learning!");
}
public static void main(String[] args) {
hello();
}
}
Collection is a group of objects which can be represented as a single unit. Collections are introduced to bring a unified common interface to all the objects.
Collection Framework was introduced since JDK 1.2 which is used to represent and manage Collections and it contains:
This framework also defines map interfaces and several classes in addition to Collections.
| Collection | Description |
|---|---|
| Set | Set is a collection of elements which can not contain duplicate values. Set is implemented in HashSets, LinkedHashSets, TreeSet etc |
| List | List is a ordered collection of elements which can have duplicates. Lists are classified into ArrayList, LinkedList, Vectors |
| Queue | FIFO approach, while instantiating Queue interface you can either choose LinkedList or PriorityQueue. |
| Deque | Deque(Double Ended Queue) is used to add or remove elements from both the ends of the Queue(both head and tail) |
| Map | Map contains key-values pairs which don't have any duplicates. Map is implemented in HashMap, TreeMap etc. |