Test 1 Review Sheet

General Computer and Programming Concepts

• Components (CPU, RAM, disk storage, I/O devices)
• bits and bytes
• evolution of programming languages
• interpreted vs. compiled languages
• Steps involved in software development
• Basic background of Java
• syntax vs semantics

Building Basic Java Programs

• A Java source file must end with the extension .java and should have the exact same name as the public class name.
• To compile a class in a Java source code file (say Yadda.java) type:
  javac Yadda.java
• Each class (there may be more than one) in a source code file, is compiled into a .class file.
• To execute a java application (say named Yadda.class) type
  java Yadda
• The main method has the following signature
  public static void main(String[] args)
• Single line comments in Java start with //
  Block-style comments in Java start with /* and end with */

Basic Elements

• Identifiers are the user-defined names in programming. (ex: variables, constants, methods, classes, labels, packages, etc.)
  • Made up of characters letters, underscores (_), dollar signs ($), or digits.
  • Must NOT start with a digit as the first character
  • Must not be a reserved word
  • Case Sensitive
• Built-in (primitive) types (boolean, char, byte, short, int, long, float, double)
• Literals:
  • integer, floating-point (double, float), character, string
  • Escape sequences for special characters
    • used for writing character literals, and used in string literals
    • Know the common ones

Operators:

• General Concepts
  • operators and operands
  • Arity (unary, binary, ternary)
  • Precedence and associativity
  • Cascading
• Arithmetic operators: + - / * %
  • understand int vs. floating-point division (/ and %)
• increment and decrement: ++ --
• Post-increment vs. Pre-increment: x++ vs. ++x
• Post-decrement vs. Pre-decrement: x-- vs. --x
• assignment operator: =(single equal sign)
  • Understand the concept of L-value vs R-value
• Other shortcut operators: += -= *= /= %=
• automatic type conversions -- know which ones are allowed
• cast operations for explicit type-conversion
• Logical operators: == != < <= > >=
• Boolean operators: && (AND), || (OR), ! (NOT)
  • short-circuit evaluation of && and ||

Console I/O

• System.out -- standard output (object of type PrintStream)
• Understand how to do console output with System.out, including the methods:
  • print()
  • println()
  • printf()
• Simple string concatenation
• System.in -- standard input
• Be able to do basic console input with the Scanner class, reading from System.in

Control Structures

• Flow of Control concepts:
  • sqeuential
  • Selection (branching)
  • Repetition (looping)
• The if/else selection statement
  • Syntax format and rules for if and for if/else statements
  • How the test expression is evaluated
  • Syntax vs. readability conventions (indentation, etc)
  • Know when to use a block
• The switch selection statement
  • Keywords switch, case, default, break
  • Understand how switch blocks work
  • only works with integer and character expressions
  • know when to use break
• Conditional operator
  • Special operator that acts similar to if-statements
  • Three operands (ternary operator)
  • Operator consists of three parts, separated by symbols: ? :
  • Example: x = (y < 0 ? 5 : 10);
• while and do-while loops
  • Syntax format and rules for both
  • How the test expression is evaluated
  • Know the difference between while and do-while
  • Know when to use a block
  • Know when the loop repeats and when it quits
• for loops
  • Three parts to the header: initial condition, test expression, iterative expression
  • Good for counting-controlled loops
  • scope of loop control variable (if declared inside header)
• Special statements affecting loop control
  • break
  • continue
• Remember: In Java, the test expression of an if-statement (and in loops) must be a boolean expression -- i.e. some operation or phrase that returns a boolean value.

Using Java Libraries

• Know the basic SDK library organization: classes grouped into packages
• Know how and when to use the import statement
  • Remember, everything from java.lang is automatically imported into every Java program
• Understand the items in the API description of a Java class library:
  • Field summary
  • Constructor summary
  • Method summary
• Know the difference between static members of a class and instance members
• Know that for static members, you call them through the class name and dot-operator:

    ClassName.member
  

• Know that for instance members, you have to create an object first
• Know how to create a basic object using a class type:

    ClassName variableName = new ClassName(arguments);
  

• Know how to call an instance member (data or method) through that object:

    objectName.member
  

• Know how to use the basic libraries that we've looked at in examples, including:
  • java.lang.Math
  • java.util.Scanner
  • java.util.Random

Methods (i.e. functions)

Method Basics

• Know what a method is
• Reasons for writing methods (divide-and-conquer, reusability)
• Perspective: builder vs. caller

Using Methods

• Know how to call a method
  • syntax
  • passing arguments
  • using the returned value
• Understand how they are like mathematical functions
• Predefined methods
  • methods in libraries
  • static vs. instance -- know the difference in the call syntax

Building Methods

• Prototype -- name, return type, parameter list
  • Know the format
  • Know what to specify in the parameter list
• Header includes modifiers (like public and static), as well as prototype
• Definition -- header, along with method body
  • the keyword return -- returning values from methods
  • using the formal parameters in the method
• Scope (and how it relates to methods)
  • Meaning of scope
  • Variables local to function blocks
  • Variables local to internal blocks (like loop bodies)
  • Scope of method parameters
• void as a return type
• Empty parameter lists
• Method overloading - methods with same name and different parameter lists