Tutorial 1
git add filename1, filename2, ...
git commit -m commit_message
git push
git pull
git status
git log (or git log --oneline)
} to describe code blocksmalloc, free)
Ensure you have the correct Java extensions installed
Ensure that you open the correct folder
example: cs2511-project
Good
Bad
Name of folder open
The folder I want to actually open
Ensure that you open the correct folder
example: cs2511-project
Good
Bad
Name of folder open
The folder I want to actually open
Ensure that you are running code using the "Run" button
Always use this to run code in this course
HelloWorld.java
Make a simple Java program that prints "Hello World" in the HelloWorld class.
package example;
/**
* Prints "Hello World" to the console.
*/
public class HelloWorld {
public static void main(String[] args) {
// Does it need a \n?
// No, .println appends a \n to your string when it prints
System.out.println("Hello World");
}
}
Sum.java
Inside a new file called Sum.java, write a program that uses the Scanner class which reads in a line of numbers separated by spaces, and sums them.
package example;
import java.util.Arrays;
import java.util.Scanner;
/**
* Write a program that uses the `Scanner` class
* which reads in a line of numbers separated by spaces,
* and sums them.
*/
public class Sum {
public static void main(String[] args) {
/**
* new - Creates a new Scanner object. (Think of it like C Malloc, but Java's
* garbage collection frees it)
* Scanner is an object that allows us to specify an input
* System.in == stdin in C
*/
Scanner scanner = new Scanner(System.in);
/**
* Keeps reading input until it sees a \n
*
* Splits each string into an array of strings
*/
String[] numbers = scanner.nextLine().split(" ");
int sum = 0;
for (String number : numbers) {
sum += Integer.parseInt(number);
}
System.out.println("The sum is " + sum);
// Advanced
// Using streams
int streamSum = Arrays.asList(numbers).stream().mapToInt(x -> Integer.parseInt(x)).sum();
System.out.println(String.format("The sum is %d", streamSum));
/**
* Frees I/O resources
* Java's garbage collector only manages memory, not other resources
*/
scanner.close();
}
}
Loop.java
public class LoopExample {
public static void main(String[] args) {
String[] myStrings = { "Hello", "World", "No" };
// Index based looping
for (int i = 0; i < myStrings.length; i++) {
String current = myStrings[i];
System.out.println(current);
}
// For-range / for-in loop
for (String current : myStrings) { // Very python like
System.out.println(current);
}
}
}Why do we use classes?
Ignoring OOP, Inheritance, Polymorphism, classes are useful for:
Shouter.java
Inside a new file Shouter.java, Write a program that stores a message and has methods for getting the message, updating the message and printing it out in all caps. Write a main() method for testing this class.
package example;
public class Shouter {
private String message;
public Shouter(String message) {
this.message = message;
}
public String getMessage() {
// NOTE: You don't have to use the keyword `this`
// But I use it because of clarity
return this.message;
}
public void setMessage(String newMessage) {
this.message = newMessage;
}
public String toString() {
return String.format("Shouter message = %s", this.message);
}
public void printMe() {
System.out.println(this.message);
}
public void shout() {
System.out.println(this.message.toUpperCase());
}
public void printAndShout() {
// NOTE: You don't have to use the keyword `this`
// But I use it because of clarity
this.printMe();
this.shout();
}
public static void main(String[] args) {
Shouter s = new Shouter("This is my message");
s.printMe();
s.shout();
// When printing objects, Java will try and stringify
// In this case, it calls the .toString() method
System.out.println(s);
}
}