Java programming

Try this

1. Type the Hello program from this lesson with your own name, compile it with javac Hello.java and run it with java Hello, then list the files in the folder to find the Hello.class file that javac created.
2. Rename the class in Hello.java to Greeting without renaming the file, compile it, and copy the error message into your notebook; then fix it so that the file name and the public class name match exactly.
3. Open a command prompt and run java -version and javac -version to note the Java version installed, then write a program that prints your name, your course and today's date (typed in as text) on three lines with println, followed by one line built from two print calls.

Try this

1. Write a program that declares one variable of each of the eight primitive types with a sensible value, such as a long mobile number with the L suffix and a float rate with the f suffix, and prints them all; then remove the f from the float value and note the compiler error.
2. Write a program that works out simple interest on a principal of 1_00_000 rupees at 7.5 percent a year for 3 years using double variables and a final constant for the rate, and prints the interest and the total amount; check that the interest comes to 22500.0.
3. In your notebook, predict what System.out.println prints for 10 / 4, 10 / 4.0, 10 % 4, (int) 9.99, "Sum: " + 2 + 3 and 2 + 3 + " items", then print them all in a program and compare the results with your predictions.

Try this

1. Write a program that reads marks out of 100 with Scanner and prints a grade with an if, else if and else ladder, printing Invalid for any mark below 0 or above 100.
2. Write a program that reads a three-letter day name such as MON or SAT and uses an arrow-style switch expression to store Weekday or Weekend in a String; then rewrite it as a classic switch with break statements and check that both versions give the same answer for all seven days.
3. Write a program that reads whole numbers with nextInt inside a do-while loop until the user enters 0, and then prints how many numbers were entered (not counting the 0), their sum and the largest of them.

Try this

1. Store a week's daily sales in an int array, print the total and the daily average using an enhanced for loop, then sort the array with Arrays.sort, print it with Arrays.toString, and print the lowest and highest values from its first and last elements.
2. Write a program that reads a full name with nextLine and prints its length, the name in capital letters, its first character, the position of the first space found with indexOf, and the first name taken out with substring; if indexOf returns -1 because there is no space, print the whole name as the first name instead of calling substring, which would throw an exception.
3. Write a program that reads one word with next(), builds its reverse with a StringBuilder by appending characters from the last index to the first with charAt, and uses equalsIgnoreCase to report whether the word is a palindrome; test it with Malayalam and Delhi.

Try this

1. Write a class Book with private fields title, author and price, a constructor that uses this to copy its parameters into the fields, and a getter for each field, then create three Book objects in main and print their details.
2. Add a setter setPrice to your Book class that refuses a negative price and prints a message instead, and add a second constructor that takes only a title and calls the first one with this(...), passing Unknown as the author and 0 as the price.
3. Add a private static int counter to Book that goes up by one in the constructor and a static method that returns it, and print it after creating your books; then make two StringBuilder variables refer to the same object, change it through one and print it through the other.

Try this

1. Type the Payroll program from this lesson, add a third subclass Intern that is paid a fixed stipend, and add one Intern to the staff array without changing the loop that prints the staff.
2. Write an interface Shape with a method double area(), implement it in classes Circle and Rectangle using @Override (declare each area() public, because interface methods are public and a class cannot make them less accessible), store one of each in a Shape array and print every area in a loop; then misspell area in one class and note what the @Override annotation makes the compiler report.
3. Create a folder named billing containing a public class Invoice whose first line is package billing; and give it one public method and one method with no access modifier; then use Invoice from a class outside the folder with import billing.Invoice; compile both from the folder above billing, and note which of the two methods you can call.

Try this

1. Write a program that reads two values as text, converts them with Integer.parseInt and divides the first by the second inside try, with separate catch blocks for NumberFormatException and ArithmeticException and a finally block that prints Done; test it with 20 and 4, 20 and 0, and 20 and abc.
2. Write a method withdraw(double amount) that throws an IllegalArgumentException with a clear message when the amount is zero or negative, call it from main inside try with one valid and one negative amount, and print the message in the catch block with getMessage().
3. Write a shopping-list program that adds five items to an ArrayList of String, removes one, uses contains to check whether Milk is on the list and prints the size; then store each item's price in a HashMap of String to Integer and print the total bill using getOrDefault.