Lecture 2: Java vs. Python

Today, we’ll learn more about Java by comparing it to what we already know about Python.

What we need for a Java program

Every Java program must define a class, and all code is inside a class
Everything in Java must have a type
Every Java program must have a function called ‘public static void main(String[] args)’
a dissected java program
Semicolons and curly braces ({}) are needed to end statements and define code blocks

Eclipse hints & Java conventions

Check the “public static void main(String[] args)” box to automatically create a main method
Java classes should start with capital letter

Data types in Java

Primitive data types (int, char, etc)
Classes & objects
String class

Comparing a Python program and a Java program

The following Python program gets a temperature in Fahrenheit from the user and prints it in Celcius.

def main():
    fahr = int(input("Enter the temperature in F: "))
    cel = (fahr - 32) * 5.0/9.0
    print("the temperature in C is: ", cel)

main()

What’s going on behind the IDE?

You can run Python in the interpreter…but not Java programs
Java is compiled

Files used in class