// IfStatements.java

class IfStatements {
	
	public static void main(String[] args) {
		// declare variables
		int x, y;

		// explain what the program does
		System.out.println("This program demonstrates if statements in Java.");
		System.out.println("Here are some examples:");

		// example #1:  A simple 'if/else' statement
		System.out.println();
		System.out.println("#1.  Simple 'if/else' statement testing if a point is");
		System.out.println("     on the line y = 2x + 3.");
		System.out.println();
		System.out.print("Enter x: ");
		x = readInt();
		System.out.print("Enter y: ");
		y = readInt();
		if (y == 2*x + 3) {
			System.out.println("This point DOES lie on the line.");
		}
		else {
			System.out.println("This point DOES NOT lie on the line.");
		}
		
		// example #2:  Another 'if/else' statement
		System.out.println();
		System.out.println("#2.  Another 'if/else' statement testing if number");
		System.out.println("     is even or odd");
		System.out.println();
		System.out.print("Enter x: ");
		x = readInt();
		if (x % 2 == 0) {
			System.out.println("That number is EVEN");
		}
		else {
			System.out.println("That number is ODD.");
		}

		// example #3:  An 'if/else-if/else' statement
		System.out.println();
		System.out.println("#2.  An 'if/else-if/else' statement testing if number");
		System.out.println("     is positive, negative, or zero.");
		System.out.println();
		System.out.print("Enter x: ");
		x = readInt();
		if (x > 0) {
			System.out.println("That number is POSITIVE");
		}
		else if (x < 0) {
			System.out.println("That number is NEGATIVE.");
		}
		else {
			System.out.println("That number is ZERO.");
		}
	}
	
	///////////////////////////////////
	// readString, readInt, readDouble
	///////////////////////////////////
	
	public static String readString() {
		java.io.InputStreamReader isr = new java.io.InputStreamReader(System.in);
		java.io.BufferedReader d = new java.io.BufferedReader(isr);
		try { return d.readLine(); } catch (Exception e) { return "error"; }
	}
	public static int readInt() { return Integer.parseInt(readString()); }
	public static double readDouble() {
		return Double.valueOf(readString()).doubleValue();
	}
}