Formatting Console Output

General Overview

• Console output in Java can often require specific formatting for readability and presentation purposes.

Using printf and format Methods

Purpose

• To display numbers in a desired format.

• Example:

  • double investment = 986.236548;

Syntax

• System.out.printf(format, item1, item2, ...);

• System.out.format(format, item1, item2, ...);

  • format: a string that may consist of substrings and format specifiers.

  • format specifier: determines how an item should be displayed and begins with a percent sign (%) and can represent numeric values, characters, or Booleans.

Format Specifiers with Examples

1. Integer in 8 spaces:

   • System.out.printf("%8d", numCourses);

2. Floating-point numbers with 2 decimals in 10 spaces:

   • System.out.printf("%10.2f", cost);

3. String in 12 spaces:

   • System.out.printf("%12s", aWord);

Frequently-Used Format Specifiers

• %b: boolean value (true/false)

• %c: character

• %d: decimal integer

• %f: floating-point number

• %e: standard scientific notation

• %s: string

Formatting Specifiers of Boolean Values

• %b: basic format

  • Example: System.out.printf("%b", isGrad);

• %nb: format with n output spaces, right-justified

Formatting Specifiers of Character Values

• %c: basic format

  • Example: System.out.printf("%c", aCharacter);

• %nc: n output spaces, right justified

Formatting Specifiers of Integer Values

• %d: basic format

  • Example: System.out.printf("%d", k);

• %nd: n output spaces, right justified

Formatting Specifiers of Floating-point Values

• %f: basic format

  • Example: System.out.printf("%f", cost);

• %n.kf: n output spaces, k digits after the decimal point, right justified

Formatting Specifiers for Scientific Values

• %e: basic format

  • Example: System.out.printf("%e", cost);

• %n.kf: n output spaces, k digits after the floating point, right justified

Formatting Specifiers for String Values

• %s: basic format

  • Example: System.out.printf("%s", aWord);

• %ns: n output spaces, right justified

Notes on Format Specifiers

• Automatically increases space if an item requires more than the specified width.

• Format strings can include substrings for additional information.

Print a New Line

• Use "
  " at the end of the format string to print a new line after the output.

Important Output Items and Justification

• Output alignment is right justified by default; left justification is indicated with a minus sign.

• If an item requires more output spaces than specified, the width is adjusted automatically.

Getting Current Time

• Use Calendar class to get current date/time and format output appropriately.

• Example:

  • System.out.printf("%tB %te, %tY%n", b, b, b);

Chapter 4: Mathematical Functions, Characters, and Strings

Objectives

• Introduce mathematical functions, characters, strings, and their application in Java.

Mathematical Functions in Java

• The Math class is essential for performing mathematical operations.

  • Common Functions include pow(a, b), sqrt(a), and more.

  • Constants such as Math.PI, Math.E for various computations.

Character Data Type and Operations

• Represents a single character.

• Character literals are enclosed in single quotes.

Commonly Used Character Encoding

• Unicode and ASCII are the common encoding schemes. Examples of how characters are represented in both formats.

String Data Type

• Represents a sequence of characters, distinguished by enclosing in double quotes.

• String methods can be performed like length(), charAt(index), toUpperCase(), etc.

Practice Exercises

• Various exercises demonstrate the use of Java features such as mathematical computations, string manipulation, and user input reading.