Day 8 of 100 - Java: Use cases

Thoughts

The Java is there from a number of years. A lot of articles, docs, solutions are available. I find it difficult to follow what is it that I should learn about.

To my knowledge (hands-on), Java is used for

coding as high-level language for building systems,
compilers (examples, https://github.com/apache/systemds),
Java API Clients (https://cloud.google.com/java/docs/reference),
Building websites (https://github.com/JetBrains/kotlin-web-site)

Java as a API client is powerful.

Space Rocket loading project

https://github.com/j143/java-basic-space-challenge

phase-1.txt

building tools=2000
building tools=2000
building tools=2000
building tools=5000
building tools=5000
building tools=2000
building tools=1000
building tools=5000
building tools=6000
shelter equipment=5000
construction equipment=5000
plants=1000
steel=8000
books=1000
water=5000

phase-2.txt

habitat=3000
colony=5000
food=5000
habitat=3000
colony=5000
food=3000
colony=5000
food=3000

`static` keyword

Static fields

// Person.java
public class Person {
    public static int instanceCount;
    public int localCount;

    public Person() {
        instanceCount++;
        localCount++;
    }

}

//Main.java
public class Main {
    public static void main(String [] args) {
        for(int i=0; i < 4; i++) {
            Person person = new Person();
            System.out.println("(" + person.localCount + ", " + + person.instanceCount + ")");
        }
    }
}

output will be: (1, 4)

Static Method

Like static fields, static methods belong to class not objects.

Points:

This is a method independent of the object
A static method takes in input arguments and returns result based on input only nothing else
The static method does not need any field values
But, a static method can still access static fields since they belong the Class

public class Compute {
  public static int add(int x, int y) {
    return x + y;
  }

  public static int subtract(int x, int y) {
    return x - y;
  }
}