added old projects

CS101/lab_20/.vscode/settings.json

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+{
+    "java.project.sourcePaths": ["src"],
+    "java.project.outputPath": "bin"
+}

CS101/lab_20/README.md

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+## Getting Started
+
+Welcome to the VS Code Java world. Here is a guideline to help you get started to write Java code in Visual Studio Code.
+
+## Folder Structure
+
+The workspace contains two folders by default, where:
+
+- `src`: the folder to maintain sources
+- `lib`: the folder to maintain dependencies
+
+Meanwhile, the compiled output files will be generated in the `bin` folder by default.
+
+> If you want to customize the folder structure, open `.vscode/settings.json` and update the related settings there.
+
+## Dependency Management
+
+The `JAVA PROJECTS` view allows you to manage your dependencies. More details can be found [here](https://github.com/microsoft/vscode-java-dependency#manage-dependencies).

CS101/lab_20/src/Animal.java

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+import javax.management.RuntimeErrorException;
+
+public abstract class Animal
+{
+	//TODO: private member variables
+	private String _soundMade;
+	private String _type;
+	private boolean _hasLegs;
+	private boolean _hasWings;
+	private boolean _hasGills;
+	
+	public Animal( String soundMade, boolean hasLegs, boolean hasWings, boolean hasGills, String type)
+	{
+		_soundMade = soundMade;
+		_hasLegs = hasLegs;
+		_hasWings = hasWings;
+		_hasGills = hasGills;
+		_type = type;
+	}
+
+	public String getType() 
+	{
+		return _type;
+	}
+	
+	public String getSoundMade()
+	{
+		return _soundMade;
+	}
+
+	public boolean hasLegs()
+	{
+		return _hasLegs;
+	}
+
+	public boolean hasWings()
+	{
+		return _hasWings;
+	}
+
+	public boolean hasGills()
+	{
+		return _hasGills;
+	}
+	public abstract int numberOfLegs();
+	public abstract int numberOfWings();
+	public abstract void breatheUnderwater();
+
+	public void PrintDetails(Animal a) {
+		String type = getType();
+		try {
+			int legs = numberOfLegs();
+			System.out.println("A " + type + " has " + legs + " legs");
+		} catch(RuntimeException e) {}
+		try {
+			int wings = numberOfWings();
+			System.out.println("A " + type + " has " + wings + " wings");
+		} catch(RuntimeException e) {}
+		try {
+			breatheUnderwater();
+		} catch(RuntimeException e) {}
+		try {
+			String sound = getSoundMade();
+			System.out.println("A " + type + " makes the sound " + sound);
+		} catch (RuntimeException e) {}
+	}
+}

CS101/lab_20/src/Bird.java

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+public class Bird extends Animal {
+    public Bird() {
+        super("tweet", true, true, false, "Bird");
+    }
+    
+    @Override
+    public void breatheUnderwater() {
+        throw new RuntimeException( "Birds can't breathe under water!");
+    }
+
+    @Override
+    public int numberOfLegs() {
+        return 2;
+    }
+
+    @Override
+    public int numberOfWings() {
+        return 2;
+    }
+}

CS101/lab_20/src/Cat.java

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+public class Cat extends Animal {
+    public Cat() {
+        super("meow", true, false, false, "Cat");
+    }
+    
+    @Override
+    public void breatheUnderwater() {
+        throw new RuntimeException( "Cats can't breathe under water!");
+    }
+
+    @Override
+    public int numberOfLegs() {
+        return 4;
+    }
+
+    @Override
+    public int numberOfWings() {
+        throw new RuntimeException("Cats don't have wings!");
+    }
+}

CS101/lab_20/src/Dog.java

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+public class Dog extends Animal {
+    
+    public Dog() {
+        super("woof", true, false, false, "Dog");
+    }
+    
+    @Override
+    public void breatheUnderwater() {
+        throw new RuntimeException( "Dogs can't breathe under water!");
+    }
+
+    @Override
+    public int numberOfLegs() {
+        return 4;
+    }
+
+    @Override
+    public int numberOfWings() {
+        throw new RuntimeException("Dogs don't have wings!");
+    }
+}

CS101/lab_20/src/Fish.java

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+public class Fish extends Animal{
+    public Fish() {
+        super("blub", false, false, true, "Fish");
+    }
+    
+    @Override
+    public void breatheUnderwater() {
+        System.out.println("A fish can breathe under water");
+    }
+
+    @Override
+    public int numberOfLegs() {
+        throw new RuntimeException("Fish don't have legs!");
+    }
+
+    @Override
+    public int numberOfWings() {
+        throw new RuntimeException("Fish don't have wings!");
+    }
+}

CS101/lab_20/src/Fox.java

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+public class Fox extends Animal {
+    public Fox() {
+        super("Ring-ding-ding-dingeringeding", true, false, false, "Fox");
+    }
+    
+    @Override
+    public void breatheUnderwater() {
+        throw new RuntimeException( "Foxes can't breathe under water!");
+    }
+
+    @Override
+    public int numberOfLegs() {
+        return 4;
+    }
+
+    @Override
+    public int numberOfWings() {
+        throw new RuntimeException("Foxes don't have wings!");
+    }
+}

CS101/lab_20/src/Tester.java

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+import java.util.ArrayList;
+
+public class Tester
+{
+	public static void main( String[] args )
+	{
+		Dog  d = new Dog () ;
+		Cat  c = new Cat () ;
+		Bird b = new Bird() ;
+		Fish f = new Fish() ;
+		Fox  x = new Fox () ;
+		
+		ArrayList<Animal> animals = new ArrayList<>();
+		animals.add(d);
+		animals.add(c);
+		animals.add(b);
+		animals.add(f);
+		animals.add(x);
+
+		for (Animal a:animals) {
+			a.PrintDetails(a);
+		}
+		}
+}