Added java/collections and java/error handling sample code

21 files changed, 465 insertions, 0 deletions

diff --git a/java/10-collections/.gitignore b/java/10-collections/.gitignore
new file mode 100644
index 0000000..e493dd6
--- /dev/null
+++ b/java/10-collections/.gitignore
@@ -0,0 +1,2 @@
+bin
+dist
diff --git a/java/10-collections/Customer.java b/java/10-collections/Customer.java
new file mode 100644
index 0000000..97fbf9f
--- /dev/null
+++ b/java/10-collections/Customer.java
@@ -0,0 +1,48 @@
+public class Customer {
+	private String name;
+
+	public Customer(String name) {
+		super();
+		this.name = name;
+	}
+
+	public String getName() {
+		return name;
+	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	@Override
+	public String toString() {
+		return "Customer [name=" + name + "]";
+	}
+
+	@Override
+	public int hashCode() {
+		final int prime = 31;
+		int result = 1;
+		result = prime * result + ((name == null) ? 0 : name.hashCode());
+		return result;
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (obj == null)
+			return false;
+		if (getClass() != obj.getClass())
+			return false;
+		Customer other = (Customer) obj;
+		if (name == null) {
+			if (other.name != null)
+				return false;
+		} else if (!name.equals(other.name))
+			return false;
+		return true;
+	}
+
+
+}
diff --git a/java/10-collections/Test1.java b/java/10-collections/Test1.java
new file mode 100644
index 0000000..d0b8660
--- /dev/null
+++ b/java/10-collections/Test1.java
@@ -0,0 +1,29 @@
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+
+public class Test1 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		List list = new ArrayList();
+//		List list = new LinkedList();
+		
+		list.add(new Customer("Nuwan"));
+		list.add(new Customer("Lasitha"));
+		list.add(new Customer("Praveen"));
+//		list.add(new Object());
+		
+		Iterator itr = list.iterator();
+		while(itr.hasNext()) {
+			Object obj = itr.next();
+			Customer c = (Customer) obj;
+			// Do some work with c here
+			System.out.println(c);
+		}
+	}
+
+}
diff --git a/java/10-collections/Test2.java b/java/10-collections/Test2.java
new file mode 100644
index 0000000..94c7234
--- /dev/null
+++ b/java/10-collections/Test2.java
@@ -0,0 +1,27 @@
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+
+public class Test2 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		List<Customer> list = new ArrayList<Customer>();
+//		List<Customer> list = new LinkedList<Customer>();
+		
+		list.add(new Customer("Nuwan"));
+		list.add(new Customer("Lasitha"));
+		list.add(new Customer("Praveen"));
+//		list.add("absdf");
+		
+		Iterator<Customer> itr = list.iterator();
+		while(itr.hasNext()) {
+			Customer c = itr.next();
+			// Do some work with c here
+			System.out.println(c);
+		}
+	}
+}
diff --git a/java/10-collections/Test3.java b/java/10-collections/Test3.java
new file mode 100644
index 0000000..57e5e47
--- /dev/null
+++ b/java/10-collections/Test3.java
@@ -0,0 +1,22 @@
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+public class Test3 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		List<Customer> list = new ArrayList<Customer>();
+		
+		list.add(new Customer("Nuwan"));
+		list.add(new Customer("Lasitha"));
+		list.add(new Customer("Praveen"));
+		
+		for (Customer c : list) {
+			// Do some work with c here
+			System.out.println(c);
+		}
+	}
+}
diff --git a/java/10-collections/Test4List.java b/java/10-collections/Test4List.java
new file mode 100644
index 0000000..c730a80
--- /dev/null
+++ b/java/10-collections/Test4List.java
@@ -0,0 +1,38 @@
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+
+public class Test4List {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		List<Customer> list = new ArrayList<Customer>();
+
+//		List<Customer> syncList = Collections.synchronizedList(list);
+		
+		list.add(new Customer("Nuwan"));
+		list.add(new Customer("Lasitha"));
+		list.add(new Customer("Praveen"));
+		
+		Customer x = list.get(2);
+		System.out.println(x);
+		
+//		list.
+		list.add(2, new Customer("Kamal"));
+		
+		Customer y = new Customer("ABC");
+		Customer z = new Customer("ABC");
+		
+		list.add(y);
+		list.add(y);
+		list.add(z);
+		
+		for (Customer c : list) {
+			// Do some work with c here
+			System.out.println(c);
+		}
+	}
+}
diff --git a/java/10-collections/Test5Set.java b/java/10-collections/Test5Set.java
new file mode 100644
index 0000000..8f182c4
--- /dev/null
+++ b/java/10-collections/Test5Set.java
@@ -0,0 +1,30 @@
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
+
+public class Test5Set {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		Set<Customer> customers = new HashSet<Customer>();
+		
+		customers.add(new Customer("Nuwan"));
+		customers.add(new Customer("Lasitha"));
+		customers.add(new Customer("Praveen"));
+		
+		Customer y = new Customer("ABC");
+		Customer z = new Customer("ABC");
+		customers.add(y);
+		customers.add(y);
+		customers.add(z);
+		
+		for (Customer c : customers) {
+			// Do some work with c here
+			System.out.println(c);
+		}
+	}
+}
diff --git a/java/10-collections/Test6Map.java b/java/10-collections/Test6Map.java
new file mode 100644
index 0000000..77ce613
--- /dev/null
+++ b/java/10-collections/Test6Map.java
@@ -0,0 +1,19 @@
+import java.util.HashMap;
+import java.util.Map;
+
+public class Test6Map {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		
+		Map<String, Customer> customers  = new HashMap<String, Customer>();
+//		Map<Integer, Account> accounts = ...
+		
+		customers.put("nugegoda", new Customer("Kamal"));
+		customers.put("kalubowila", new Customer("Praveen"));
+		
+		System.out.println(customers.get("kalubowila"));
+	}
+}
diff --git a/java/10-collections/hashcode-contract.txt b/java/10-collections/hashcode-contract.txt
new file mode 100644
index 0000000..2ed248c
--- /dev/null
+++ b/java/10-collections/hashcode-contract.txt
@@ -0,0 +1,15 @@
+   Whenever it is invoked on the same object more than once during an execu-
+   tion of a Java application, the hashCode() method must consistently return
+   the same integer, provided no information used in equals() comparisons
+   on the object is modified. This integer need not remain consistent from one
+   execution of an application to another execution of the same application.
+   
+   If two objects are equal according to the equals(Object) method, then
+   calling the hashCode() method on each of the two objects must produce the
+   same integer result.
+   
+   It is NOT required that if two objects are unequal according to the
+   equals(java.lang.Object) method, then calling the hashCode() method
+   on each of the two objects must produce distinct integer results. However,
+   the programmer should be aware that producing distinct integer results for
+   unequal objects may improve the performance of hashtables.
diff --git a/java/11-error-handling-1/.gitignore b/java/11-error-handling-1/.gitignore
new file mode 100644
index 0000000..e493dd6
--- /dev/null
+++ b/java/11-error-handling-1/.gitignore
@@ -0,0 +1,2 @@
+bin
+dist
diff --git a/java/11-error-handling-1/ErrorHandlingExample1.java b/java/11-error-handling-1/ErrorHandlingExample1.java
new file mode 100644
index 0000000..0dc0276
--- /dev/null
+++ b/java/11-error-handling-1/ErrorHandlingExample1.java
@@ -0,0 +1,20 @@
+public class ErrorHandlingExample1 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		int x = 2;
+		int y = 0;
+		int z = 0;
+
+//		try {
+		    z = x / y;
+//		} catch (ArithmeticException ae) {
+//			System.out.println("An error occurred");
+//		}
+		
+		System.out.println(z);
+	}
+
+}
diff --git a/java/12-error-handling-2/.gitignore b/java/12-error-handling-2/.gitignore
new file mode 100644
index 0000000..e493dd6
--- /dev/null
+++ b/java/12-error-handling-2/.gitignore
@@ -0,0 +1,2 @@
+bin
+dist
diff --git a/java/12-error-handling-2/Maths.java b/java/12-error-handling-2/Maths.java
new file mode 100644
index 0000000..b61a9f2
--- /dev/null
+++ b/java/12-error-handling-2/Maths.java
@@ -0,0 +1,11 @@
+public class Maths {
+	
+	public int factorial(int number) throws MathsException {
+		if (number < 0) {
+			MathsException e = new MathsException("Factorial of " + number + " not defined");
+//			e.setX(100);
+			throw e;
+		}
+		return number == 0 ? 1 : number * factorial(number - 1); 
+	}
+}
diff --git a/java/12-error-handling-2/MathsException.java b/java/12-error-handling-2/MathsException.java
new file mode 100644
index 0000000..bdbaf81
--- /dev/null
+++ b/java/12-error-handling-2/MathsException.java
@@ -0,0 +1,22 @@
+public class MathsException extends Exception {
+
+	public MathsException() {
+		// TODO Auto-generated constructor stub
+	}
+
+	public MathsException(String message) {
+		super(message);
+		// TODO Auto-generated constructor stub
+	}
+
+	public MathsException(Throwable cause) {
+		super(cause);
+		// TODO Auto-generated constructor stub
+	}
+
+	public MathsException(String message, Throwable cause) {
+		super(message, cause);
+		// TODO Auto-generated constructor stub
+	}
+
+}
diff --git a/java/12-error-handling-2/MathsTest.java b/java/12-error-handling-2/MathsTest.java
new file mode 100644
index 0000000..7b6827c
--- /dev/null
+++ b/java/12-error-handling-2/MathsTest.java
@@ -0,0 +1,32 @@
+public class MathsTest {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		Maths m = new Maths();
+		int result = 0;
+		
+		try {
+			m.factorial(-5);
+			m.factorial(5); // Not executed
+		} catch (MathsException e) {
+			// TODO Auto-generated catch block
+			e.printStackTrace();
+		}
+		
+		try {
+		    result = m.factorial(-5);
+		    // ...
+		} catch(MathsException me) {
+//			System.err.println(me.getX());
+			System.err.println("Factorial method failed");
+		} finally {
+			System.out.println("Inside finally block");
+		}
+		
+		System.out.println(result);
+		
+	}
+
+}
diff --git a/java/12-error-handling-2/MathsTest2.java b/java/12-error-handling-2/MathsTest2.java
new file mode 100644
index 0000000..4aa8b59
--- /dev/null
+++ b/java/12-error-handling-2/MathsTest2.java
@@ -0,0 +1,27 @@
+public class MathsTest2 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		Maths m = new Maths();
+		int result = 0;
+		
+		try {
+		    result = m.factorial(-5);
+		} catch(MathsException me) { // Catching a specific exception
+			System.err.println("Caught a MathsException");
+		} catch(Exception e) { // Catching the super type
+			System.err.println("Caught an Exception");
+		}
+		
+		try {
+			result = m.factorial(-5);
+		} catch (MathsException | ArrayIndexOutOfBoundsException e) { // Java SE 7
+			
+		}
+		
+		System.out.println(result);
+	}
+
+}
diff --git a/java/12-error-handling-2/MathsTest3.java b/java/12-error-handling-2/MathsTest3.java
new file mode 100644
index 0000000..ca45e5c
--- /dev/null
+++ b/java/12-error-handling-2/MathsTest3.java
@@ -0,0 +1,21 @@
+public class MathsTest3 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		Maths m = new Maths();
+		int result = 0;
+		
+		try {
+		    result = m.factorial(-5);
+		} catch(MathsException e) {
+			System.err.println("Factorial method failed");
+			System.err.println(e.getMessage());
+			e.printStackTrace();
+		}
+		
+		System.out.println(result);
+	}
+
+}
diff --git a/java/12-error-handling-2/MathsTest4.java b/java/12-error-handling-2/MathsTest4.java
new file mode 100644
index 0000000..b5cca8a
--- /dev/null
+++ b/java/12-error-handling-2/MathsTest4.java
@@ -0,0 +1,33 @@
+public class MathsTest4 {
+
+	/**
+	 * @param args
+	 * @throws MathsException 
+	 */
+	public static void main(String[] args) throws MathsException {
+		Maths m = new Maths();
+		int result = 0;
+		
+		// No catching! Then the method should be declared
+		// to throw the exception (or a super type like
+		// Exception or even Throwable)
+		
+//		m.factorial(5);
+		
+		// Look! A try block can be defined without a catch block
+		// as well.
+		try {
+		    result = m.factorial(-5);
+		    System.out.println("xxx");
+		} finally {
+			System.out.println("Inside finally block");
+		}
+		
+		// No try block is also possible
+		// Since the method is declared to duct the exception
+		result = m.factorial(-5);
+		
+		System.out.println(result);
+	}
+
+}
diff --git a/java/12-error-handling-2/MathsTest5.java b/java/12-error-handling-2/MathsTest5.java
new file mode 100644
index 0000000..56bf64d
--- /dev/null
+++ b/java/12-error-handling-2/MathsTest5.java
@@ -0,0 +1,21 @@
+public class MathsTest5 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) throws Exception {
+		Maths m = new Maths();
+		int result = 0;
+		
+		try {
+		    result = m.factorial(-5);
+		} catch (MathsException me) {
+			throw new Exception("My exception wrapper", me);
+		} finally {
+			System.out.println("Inside finally block");
+		}
+		
+		System.out.println(result);
+	}
+
+}
diff --git a/java/12-error-handling-2/MathsTest6.java b/java/12-error-handling-2/MathsTest6.java
new file mode 100644
index 0000000..7f176aa
--- /dev/null
+++ b/java/12-error-handling-2/MathsTest6.java
@@ -0,0 +1,22 @@
+public class MathsTest6 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		Maths m = new Maths();
+		int result = 0;
+		
+		try {
+		    result = m.factorial(-5);
+		} catch(MathsException me) {
+			System.err.println("Factorial method failed");
+			System.exit(1);
+		} finally {
+			System.out.println("Inside finally block");
+		}
+		
+		System.out.println(result);
+	}
+
+}
diff --git a/java/12-error-handling-2/MathsTest7.java b/java/12-error-handling-2/MathsTest7.java
new file mode 100644
index 0000000..f55cfad
--- /dev/null
+++ b/java/12-error-handling-2/MathsTest7.java
@@ -0,0 +1,22 @@
+public class MathsTest7 {
+
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		Maths m = new Maths();
+		int result = 0;
+		
+		try {
+		    result = m.factorial(-5);
+		} catch(MathsException me) {
+			System.err.println("Factorial method failed");
+			return;
+		} finally {
+			System.out.println("Inside finally block");
+		}
+		
+		System.out.println(result);
+	}
+
+}