Bad OO Design in Java

BadDesign1.java

/**
 * @BankAccount.java
 * BankAccount is a domain object (POJO) for bank account holder.
 **/
public class BankAccount {
	private String accountNumber;
	private double accountBalance;
	private static final double interestRate = 5;
	
	public BankAccount(String accountNumber){
		this.accountNumber = accountNumber;
	}
	
	// Do interest calculation business logic
	public double calculateInterest(){
		return (interestRate * accountBalance)/100;
	}
	
	// Save money into current account business logic
	public double save(double amount){
		return accountBalance + amount;
	}
	
	// Withdraw money from current account business logic
	public double withdraw(double amount){
		return accountBalance - amount;
	}
	
	public String getAccountNumber() {
		return accountNumber;
	}
	
	public void setAccountNumber(String accountNumber) {
		this.accountNumber = accountNumber;
	}
	
	public double getAccountBalance() {
		return accountBalance;
	}
	
	public void setAccountBalance(double accountBalance) {
		this.accountBalance = accountBalance;
	}
}

public class InterestCalculator {
}

BadDesign2.java

/**
 * @Shape.java
 **/ 
public class Shape {
	static final int CIRCLE = 1;
	static final int RECTANGLE = 2;
	int TYPE = 0;
	
	private double radius;
	private double width;
	private double length;
	
	public double area() {
		switch(TYPE){
			case CIRCLE:
				return Math.PI * radius;
			case RECTANGLE:
				return width * length;
			default:
				return 0;
		}
	}

	public void createCircle(double radius) {
		this.radius = radius;
		this.TYPE = CIRCLE;
	}
	
	public void createRectangle(double width, double length){
		this.width = width;
		this.length = length;
		this.TYPE = RECTANGLE;
	}
}

BadDesign3.java

/**
 * @Shape.java
 **/
public interface Shape {
	public double area();
}

/**
 * @Rectangle.java
 **/ 
public class Rectangle implements Shape {
	private double width;
	private double length;
	
	private Rectangle(){}
	
	public Rectangle(double width, double length){
		this.width = width;
		this.length = length;
	}
	
	public double area(){
		return this.width * this.length;
	}
}

/**
 * @Square.java
 **/ 
public class Square extends Rectangle {
	private double edge;
	
	public Square(double edge) {
		super(edge, edge);
		this.edge = edge;
	}
}

BadDesign4.java

public interface Vehicle {
	void fly() throws Exception;
	void drive() throws Exception;
}

public class Car implements Vehicle {
	@Override
	public void fly() throws Exception {
		throw new Exception("Uh oh cannot fly");
	}

	@Override
	public void drive() throws Exception {
		// implement drive here
	}
}

public class Plane implements Vehicle {
	@Override
	public void fly() throws Exception {
		// implement fly here
	}

	@Override
	public void drive() throws Exception {
		throw new Exception("not good for driving");
	}
}

BadDesign5.java

/**
 * @IOutputter.java
 **/ 
public interface IOutputter {
    void print(String output);
}

/**
 * @ConsoleOutputter.java
 **/
public class ConsoleOutputter implements IOutputter {
  public void print(String output) {
    System.out.println(output);
  }
}

/**
 * @MockOutputter.java
 **/
public class MockOutputter implements IOutputter {
  public void print(String output){
    // do nothing
  }
}

/**
 * @CommandInvoker.java
 **/
public class CommandInvoker {
  public void invoke(ConsoleOutputter outputter) {
    outputter.print("Hello World");
  }
}