Basic Java Importing

This is a basic reminder on how to declare packages and import those packages when running Gradle tests.

Layout

Given the following example to test a Linked List Java class, we have the following layout for the .java and test files:

└── src
    ├── main
    │   └── java
    │       ├── LinkedList.java
    │       └── Node.java
    └── test
        └── java
            └── LinkedListTest.java
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File 1: src/main/java/LinkedList.java

import main.java.Node;

class LinkedList {
    Integer size;
    Node head;

    public LinkedList() {
        this.size = 0;
        this.head = null;
    }

    public LinkedList(Node head) {
        this.size = 1;
        this.head = head;
    }

    public Integer getSize() {
        return this.size;
    }

    public Node getFirst() {
        return this.head;
    }
}
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File 2: src/main/java/Node.java

Notice here that the package itself is has the public modifier and has the package main.java itself declared.

package main.java;

public class Node {
    private Integer data;
    private Node next;

    public Node(Integer data) {
        this.data = data;
        this.next = null;
    }

    public Node(Integer data, Node next) {
        this.data = data;
        this.next = next;
    }

    public void setNext(Node next) {
        this.next = next;
    }

    public Node getNext() {
        return this.next;
    }

    public void setData(Integer data) {
        this.data = data;
    }

    public Integer getData() {
        return this.data;
    }
}
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File 3: src/test/java/LinkedListTest.java

For this particular test, we also need to import the Node package to ensure we can create nodes for the LinkedList.

import org.junit.Ignore;
import org.junit.Test;

import static org.junit.Assert.assertEquals;
import main.java.Node;

public class LinkedListTest {
    @Test
    public void testGetFirst() {
        Node n1 = new Node(2);
        LinkedList ll = new LinkedList(n1);
        assertEquals(ll.getFirst(), n1);
    }
}
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