Teaching and Learning

Scratch to Java (Part-1)

Transitioning from block coding to text can be challenging. In this post, we'll look into the 1:1 code comparison of Scratch and Java. In the next post, we'll take a Scratch project and code it in Java.

Jane Lee

Jul 25, 2023 • 2 min read

Common challenges of transitioning from Scratch to Java:

All code blocks are visible on Scratch. However, for Java, students will have to look up the Java syntax and commands from documentation websites or by searching online.
Scratch doesn't produce syntax errors. Java on the other hand has strict syntax rules and the wrong syntax will result in errors.
Scratch produces visual results and animations. Students may find Java less engaging at first.

Level of Abstraction

Scratch to Java Code Examples

Output

System.out.println("Hello World!");

Instantiating a variable

int a = 5; 
int b = 3;

Operators

int a = 5; 
int b = 3; 
System.out.println(a + b);

Conditional Statements

if (a > 50) { 
    System.out.println("Great!"); 
}else{ 
    System.out.println("Try again!"); 
}

For loop

int a = 0; 
for (int i = 0; i < 3; i++){ 
    a = a + 1; 
}

Getting user input

import java.util.Scanner; 

public class Test { 
    public static void main(String[] args){ 
        Scanner scanObj = new Scanner(System.in); 
        System.out.println("What's your name?"); 
        String name = scanObj.nextLine(); 
        System.out.println("Hi "+ name); 
    } 
}

Function and function call

public static void main(String[] args){
    hello("Julia"); 
} 
public static void hello(String name){ 
    System.out.println("Hello " + name); 
}

Block-based program
High-level program (Java)	class Triangle { … double area(float b, float h) { return b*h/2; } ... }
Low-level program	LOAD r1, b LOAD r2, h MUL r1, r2 DIV r1, #2 RET
Executable Machine code	0000100101010001010001010 1000101010000110101001100 0101001000100010010101000 1010001010100010101000...

Scratch to Java Code Examples

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