Initial commit

.gitignore

+/.project
+/.settings
+/bin
+/.classpath

src/exercise_qa/Operators.java

+package exercise_qa;
+
+public class Operators {
+	public static void main(String[] args) {
+		int i = 10;
+		int n = i++%5;
+		
+	}
+
+}

src/java_exercises1_1_1/HelloWorld.java

+//This is my package definition
+package java_exercises1_1_1;
+
+/**
+ * Here you should place some documentation about the meaning of the classes and its general use.
+ * 
+ * This is a HelloWorld class. 
+ * @author mad
+ *
+ */
+public class HelloWorld {
+
+	/**
+	 * This is the main entry point of the application - the main function
+	 * @param args Array of String objects: refers to the parameters of the commandline
+	 */
+	public static void main(String[] args) {
+		//Prints out text to the console: "Hello World" 
+		System.out.println("Hello World");
+	}
+
+}

src/java_exercises1_1_2/DataTypes.java

+package java_exercises1_1_2;
+
+public class DataTypes {
+	//application wide static scope
+	static double myMoney=1233489390;
+
+	public static void main(String[] args) {
+		//local variable scope
+		//declare a
+		int a;
+		//define b: declare and initialize with 1
+		int b=1;
+		//define string firstName
+		String firstName="Martin";
+		//define string lastName
+		String lastName="Deinhofer";
+		//define variable pi
+		double pi=3.14159;
+		
+		//Assign a value to a
+		a=10;		
+		//print out the value to the console
+		System.out.println("a="+a);
+		
+		b=a+a;
+		System.out.println("b="+b);
+		
+		//Explicitely cast the double variable to an int variable with data loss
+		a=(int)pi;
+		System.out.println("pi="+pi+", a="+a);
+		
+		//String concatenation: Print: "My name: Martin Deinhofer"
+		System.out.println("My name: "+firstName+" "+lastName);
+		
+		//You can use myMoney variable here as well
+		System.out.println("I have a lot of money: "+myMoney);	
+	}
+
+}

src/java_exercises1_1_3/ConsoleInput.java

+package java_exercises1_1_3;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+//import statements make classes in respective packages usable without fully qualified name (without java.io. as a prefix)
+import java.io.InputStreamReader;
+
+public class ConsoleInput {
+
+	public static void main(String[] args) {
+		//Without import statements we would have to write java.io.Reader
+		//cascade of streams: System.in -> InputStreamReader -> BufferedReader
+		//BufferedReader let's us elegantly read lines of input (and not characters) directly
+		BufferedReader input=new BufferedReader(new InputStreamReader(System.in));
+		try {
+			System.out.print(">");
+			//Read line of input			
+			String line=input.readLine();			
+			
+			//You can parse it as an integer number, but if it's not numeric an exception is thrown
+			int number=Integer.valueOf(line);
+			System.out.println("Read line: "+line);
+			System.out.println("Read number: "+number);
+			
+			//You will get to know exceptions later, just use it like this for now.
+		} catch (IOException e) {
+			//In case the console input stream cannot be opened (System.in) an IOException is thrown
+			e.printStackTrace();
+			
+			//Use exceptions to inform the user about errors and to cleanup / change control flow
+			//more on this later
+			System.out.println("The input console could not be opened");
+		}
+	}
+
+}

src/java_exercises1_2_1/ArraysLoops.java

+package java_exercises1_2_1;
+
+public class ArraysLoops {
+
+	public static void main(String[] args) {
+		int n=20;
+		//declare array of size n
+		int a[]=new int[n];
+		
+		//initialize manually
+		for(int i=0;i<n;i++) {
+			//assign a value to each element of the array
+			a[i]=i;			
+			System.out.println("a["+i+"]="+a[i]);
+		}
+		
+		//now loop through all elements using the Iterator interface (no manual index needed)
+		//this way the index cannot exceed the number of elements --> less error prone!!
+		for(int elem : a) {
+			//is value dividable by 2 without rest value??
+			if((elem % 2) == 0) {
+				System.out.println("elem="+elem);
+			}
+		}
+	}
+
+}

src/java_exercises1_2_2/UserInput.java

+package java_exercises1_2_2;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+public class UserInput {
+	//a function can throw an exception indicating the caller that an exception might occur
+	//in case of the main function, the program will terminate
+	public static void main(String[] args) throws IOException {
+		//always init variables with meaningful values to prevent NullPointerException
+		String input="";
+		BufferedReader inputReader=new BufferedReader(new InputStreamReader(System.in));
+
+		do{		
+			System.out.print(">");
+			//Read line of input			
+			input=inputReader.readLine();
+			
+			//Creates a string object with value "e" and compares it's equality with the value of input			
+		}while(!"e".equals(input));		
+		System.out.println("You wanted to exit the program, good bye");
+	}
+
+}