Java practice

ch03/CelsiusToFahrenheit.java

@@ -0,0 +1,28 @@
+import java.util.Scanner;
+
+public class CelsiusToFahrenheit {
+
+    public static void main(String[] args) {
+        // Create variables
+        double celsius;
+        double fahrenheit;
+        final int FREEZING_TEMP = 32;
+        Scanner input = new Scanner(System.in);
+
+        // Ask for number in celsius, then save that input as the celsius variable
+        System.out.print("Enter a temperature in Celsius: ");
+        celsius = input.nextDouble();
+        System.out.printf("%.1f celsius\n", celsius);
+
+        // Conver celsius to fahrenheit 
+        fahrenheit = (celsius * 9.0/5.0) + (FREEZING_TEMP);
+
+        // Display result!
+        System.out.printf("%.1f celsius = %.1f fahrenheit\n", celsius, fahrenheit);
+
+
+
+    }
+
+
+}

ch03/Convert.java

@@ -12,16 +12,41 @@ public static void main(String[] args) {
         final int IN_PER_FOOT = 12;
         Scanner in = new Scanner(System.in);
 
-        // prompt the user and get the value
-        System.out.print("Exactly how many cm? ");
-        cm = in.nextDouble();
-
-        // convert and output the result
-        inches = (int) (cm / CM_PER_INCH);
-        feet = inches / IN_PER_FOOT;
-        remainder = inches % IN_PER_FOOT;
-        System.out.printf("%.2f cm = %d ft, %d in\n",
-                          cm, feet, remainder);
+        System.out.print("Enter 1 to convert centimeters to feet and inches\n"
+                         + "Enter 2 to convert feet and inches to centimeters\n"
+                         + "Your choice: ");
+
+        int choice = in.nextInt();
+
+        if (choice == 1) {
+            System.out.print("Exactly how many cm? ");
+            cm = in.nextDouble();
+
+            if (cm < 0) {
+                System.out.print("Please enter a positive value for centimeters.");
+            } else {
+                inches = (int) (cm / CM_PER_INCH);
+                feet = inches / IN_PER_FOOT;
+                remainder = inches % IN_PER_FOOT;
+                inches = inches - (feet * IN_PER_FOOT);
+                System.out.printf("%.2f cm = %d ft, %d in\n", cm, feet, inches);
+            }
+        } else if (choice == 2) {
+            System.out.print("Enter feet: ");
+            feet = in.nextInt();
+            System.out.print("Enter inches: ");
+            inches = in.nextInt();
+
+            if (feet < 0 || inches < 0 || inches >= IN_PER_FOOT) {
+                System.out.println("Please enter valid and positive values for feet and inches.");
+            } else {
+                cm = (feet * IN_PER_FOOT + inches) * CM_PER_INCH;
+                System.out.printf("%d ft, %d in = %.2f cm\n", feet, inches, cm);
+            }
+        } else {
+            System.out.println("Invalid choice, please enter 1 or 2.");
+        }
+
     }
 
 }

ch03/Echo.java

@@ -15,7 +15,11 @@ public static void main(String[] args) {
 
         System.out.print("Type something else: ");
         line = in.nextLine();
-        System.out.println("You also said: " + line);
+        System.out.println("You then said: " + line);
+
+        System.out.print("One more time please: ");
+        line = in.nextLine();
+        System.out.println("I totally agree with " + line);
     }
 
 }

ch03/Formatting.java

@@ -11,7 +11,7 @@ public static void main(String[] args) {
         // formatting output
 
         System.out.print(4.0 / 3.0);
-        System.out.printf("Four thirds = %.3f", 4.0 / 3.0);
+        System.out.printf("Four thirds = %.3f\n", 4.0 / 3.0);
 
         int inch = 100;
         double cm = inch * CM_PER_INCH;
@@ -27,7 +27,8 @@ public static void main(String[] args) {
         inch = (int) (cm / CM_PER_INCH);
         System.out.printf("%f cm = %d in\n", cm, inch);
 
-        System.out.printf("inches = %d" + inch);  // error
+
+        System.out.printf("inches = %d", inch);  // Error was a '+' sign where a comma should have been, fixed!
     }
 
 }

ch03/GuessGame.java

@@ -0,0 +1,43 @@
+import java.util.Random;
+import java.util.Scanner;
+
+/**
+ * "Guess My Number" game with added fun features.
+ */
+public class GuessGame {
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        Random random = new Random();
+
+        System.out.println("Welcome to the Guess My Number game!");
+        System.out.println("I've picked a number between 1 and 100.");
+        System.out.println("Try to guess it!");
+
+        int numberToGuess = random.nextInt(100) + 1;
+        int attempts = 0;
+        int maxAttempts = 15;
+
+        while (attempts < maxAttempts) {
+            System.out.print("Enter your guess: ");
+            int guess = scanner.nextInt();
+            attempts++;
+
+            if (guess == numberToGuess) {
+                System.out.println("Congratulations! You guessed the number in " + attempts + " attempts!");
+                break;
+            } else if (guess < numberToGuess) {
+                System.out.println("Too low! Try again.");
+            } else {
+                System.out.println("Too high! Try again.");
+            }
+        }
+
+        if (attempts == maxAttempts) {
+            System.out.println("Oops! You've reached the maximum number of attempts.");
+            System.out.println("The correct number was: " + numberToGuess);
+        }
+
+        scanner.close();
+    }
+}

ch03/ScannerBug.java

@@ -14,13 +14,14 @@ public static void main(String[] args) {
         name = in.nextLine();
         System.out.print("What is your age? ");
         age = in.nextInt();
+        in.nextLine(); // Consume the newline character after reading the age.
         System.out.printf("Hello %s, age %d\n", name, age);
 
-        in.reset();
         System.out.println();
 
         System.out.print("What is your age? ");
         age = in.nextInt();
+        in.nextLine(); // Consume the newline character after reading the age.
         System.out.print("What is your name? ");
         name = in.nextLine();
         System.out.printf("Hello %s, age %d\n", name, age);

ch04/Date.java

@@ -0,0 +1,27 @@
+
+public class Date {
+
+    public static void printAmerican(int date, int year, String day, String month) {
+        System.out.print("American format for date: ");
+        System.out.print(day);
+        System.out.print(", ");
+        System.out.print(month);
+        System.out.print(" ");
+        System.out.print(date);
+        System.out.print(", ");
+        System.out.println(year);
+
+
+    }
+
+    public static void main (String[] args) {
+        int date = 11;
+        int year = 1993;
+        String day = "Monday";
+        String month = "April";
+        printAmerican(date, year, day, month);
+
+    }
+
+}
+

ch04/IsPalindrome.java

@@ -0,0 +1,61 @@
+import java.util.Random;
+
+public class IsPalindrome {
+    public static void main(String[] args) {
+        Random random = new Random();
+        String input = generateRandomString(random, 6); 
+        boolean isPalindrome = isSpecial(input);
+        int longestPalindromeLength = getPalindromeLength(input);
+        System.out.println("Random String: " + input);
+        System.out.println("Is it a palindrome? " + isPalindrome);
+        System.out.println("Longest Palindromic Length: " + longestPalindromeLength);
+    }
+
+    public static boolean isSpecial(String text) {
+        String tempText = alterText(text);
+        return text.equals(tempText);
+    }
+
+    public static String alterText(String inputText) {
+        if (inputText == null || inputText.isEmpty()) {
+            return inputText;
+        }
+        return inputText.charAt(inputText.length() - 1) +
+                alterText(inputText.substring(0, inputText.length() - 1));
+    }
+
+    public static String generateRandomString(Random random, int length) {
+        String chars = "abcdefghijklmnopqrstuvwxyz";
+        StringBuilder sb = new StringBuilder(length);
+        for (int i = 0; i < length; i++) {
+            int randomIndex = random.nextInt(chars.length());
+            sb.append(chars.charAt(randomIndex));
+        }
+        return sb.toString();
+    }
+
+    public static int getPalindromeLength(String text) {
+        String reversed = new StringBuilder(text).reverse().toString();
+        int maxLength = 0;
+        int currentLength = 0;
+
+        for (int i = 0; i < text.length(); i++) {
+            if (text.charAt(i) == reversed.charAt(i)) {
+                currentLength++;
+                if (currentLength > maxLength) {
+                    maxLength = currentLength;
+                }
+            } else {
+                currentLength = 0;
+            }
+        }
+        return maxLength;
+    }
+
+
+
+}
+
+
+
+

ch04/Merge.java

@@ -0,0 +1,36 @@
+public class Merge {
+    public static void main(String[] args) {
+
+        // Test cases
+        int[] arr1 = { 1, 3, 5 };
+        int[] arr2 = { 2, 4, 6, 8 };
+
+        // Call the merge function to combine the two arrays
+        int[] mergedArray = merge(arr1, arr2);
+
+        // Display the merged array
+        System.out.println("Merged Array:");
+        for (int num : mergedArray) {
+            System.out.print(num + " ");
+        }
+    }
+
+    public static int[] merge(int[] a, int[] b) {
+        int[] result = new int[a.length + b.length];
+        for (int i = 0; i < a.length; i++) {
+             // Place elements from array 'a' at even indices in the result array
+            result[2 * i] = a[i];
+
+            // Check if there's a corresponding element in array 'b' to place at odd index
+            if (i < b.length) {
+                result[2 * i + 1] = b[i];
+            }
+        }
+        // If array b is longer than array a, add the remaining elements of b
+        for (int i = a.length; i < b.length; i++) {
+            result[2 * i] = b[i];
+        }
+        return result;
+    }
+}
+