Composition in Java

package anote;

class PC {
    private Case theCase;
    private Monitor monitor;
    private Motherboard motherboard;

    public PC(Case theCase, Monitor monitor, Motherboard motherboard) {
        this.theCase = theCase;
        this.monitor = monitor;
        this.motherboard = motherboard;
    }

    public Case getTheCase() {
        return this.theCase;
    }

    public Monitor getMonitor() {
        return this.monitor;
    }

    public Motherboard getMotherboard() {
        return this.motherboard;
    }

}

class Case {
    private String model;
    private String manufacturer;
    private String powerSupply;
    private Dimensions dimensions;

    public Case(String model, String manufacturer, String powerSupply, Dimensions dimensions) {
        this.model = model;
        this.manufacturer = manufacturer;
        this.powerSupply = powerSupply;
        this.dimensions = dimensions;
    }

    public void pressPowerButton() {
        System.out.println("Power button pressed");
    }

    public String getModel() {
        return this.model;
    }

    public String getManufacturer() {
        return this.manufacturer;
    }

    public String getPowerSupply() {
        return this.powerSupply;
    }

    public Dimensions getDimensions() {
        return this.dimensions;
    }
}

class Dimensions {
    private int width;
    private int height;
    private int depth;

    public Dimensions(int width, int height, int depth) {
        this.width = width;
        this.height = height;
        this.depth = depth;
    }

    public int getWidth() {
        return width;
    }

    public int getHeight() {
        return height;
    }

    public int getDepth() {
        return depth;
    }

}

class Monitor {

    private String model;
    private String manufacturer;
    private int size;
    private Resolution nativeResolution;

    public Monitor(String model, String manufacturer, int size, Resolution nativeResolution) {
        this.model = model;
        this.manufacturer = manufacturer;
        this.size = size;
        this.nativeResolution = nativeResolution;
    }

    public void drawPixelAt(int x, int y, String color) {
        System.out.print("Drawing pixel at " + x + "," + y + "in colour" + color);
    }

    public String getModel() {
        return model;
    }

    public String getManufacturer() {
        return manufacturer;
    }

    public int getSize() {
        return size;
    }

    public Resolution getNativeResolution() {
        return nativeResolution;
    }
}

class Resolution {

    private int width;
    private int height;

    public Resolution(int width, int height) {
        this.width = width;
        this.height = height;
    }

    public int getWidth() {
        return width;
    }

    public int getHeight() {
        return height;
    }
}

class Motherboard {

    private String model;
    private String manufacturer;
    private int ramSlots;
    private int cardSlots;
    private String bios;

    public Motherboard(String model, String manufacturer, int ramSlots, int cardSlots, String bios) {
        this.model = model;
        this.manufacturer = manufacturer;
        this.ramSlots = ramSlots;
        this.cardSlots = cardSlots;
        this.bios = bios;
    }

    public void loadProgram(String programName) {
        System.out.println("Program " + programName + "is now loading...");
    }

    public String getModel() {
        return model;
    }

    public String getManufacturer() {
        return manufacturer;
    }

    public int getRamSlots() {
        return ramSlots;
    }

    public int getCardSlot() {
        return cardSlots;
    }

}

public class Main {
    public static void main(String[] args) {

        Dimensions dimensions = new Dimensions(50, 50, 30);
        Case theCase = new Case("220B", "Samsung", "220", dimensions);
        Monitor monitor = new Monitor("55inch", "LG", 27, new Resolution(1680, 1050));
        Motherboard motherboard = new Motherboard("ZI70C-Gaming 7", "Gigabyte", 4, 6, "F7");
        PC pc = new PC(theCase, monitor, motherboard);
        pc.getMonitor().drawPixelAt(1500, 1200, "red");
        pc.getMotherboard().loadProgram("Mac OS");
        pc.getTheCase().pressPowerButton();
    }
}