ITEC 120: Week 9

• Tuesday:


• conditions to graduate and not graduate
• two ifs vs if else
• remembering a boolean result
• definite assignment
• statement blocks
• examples from book


• Thursday:
• Nested vs sequential if statements
• if else if else if else (eg grades)
• Equality of objects
• == compares references
• default version of .equals compares references
• specialized version of .equals compares fields


• Equality of Strings
• Use .equals
• == compares references (but strings can share references)


• Switch statements
• Similar to if else if else if else
• Use break


• Coding if else if else


• Examples: ...


• Chapter 5: Logical operators, if-else, block statements


• Logical operators combine two boolean values and produce another boolean value
• Contrast with
• Arithmetic operators combine 2 numbers and produce another number
• Relational operators compare two numeric values and produce another number


• Logical operator AND (ie &&)
• Result is true if both operands are true, false if either or both are false
• Truth table
• Example: graduation requirements: hours and gpa


• Logical operator OR (ie ||)
• Result is true if either operand is true, false if both are false
• Truth table
• Example: major and concentrations


• Logical operator NOT (ie !)
• Operates on a SINGLE value
• Unary operator vs binary operator (eg -3 + 4 shows both)
• Result is true if operand is false, and false if operand is true
• AKA logical negation and logical complement (not compliment)
• Truth table


• && and || are SHORT CIRCUIT operators: only evaluate second operand when required
• Example: if (x != 0 && 3/x > 5)


• DeMorgan's Law: !(a && b) == (!a || !b)
• DeMorgan's Law: !(a || b) == (!a && !b)
• if-else:
  • Use else to nest two statements
  • execute then part when condition is true
  • execute else part when condition is false
  • Examples:
  • Wages.java
  • CoinFlip.java
  • Coin.java
  • helps with definite assignment
  
  
• Block statements
  • A block statement is one or more statements enclosed in curly braces
  • Makes it possible to use several statements where one is required
  • Can be used as then and/or else parts
  • Guessing.java
  • Careful of indentation of multiline then or else parts
• Lab 14


• Lab 15


• Examples from Chapter 5


• Chapter 5 Powerpoint Slides


• Semester Calendar