• We want our program to be able to execute statements conditionally, based on the value of data entered by the user.
• An if structure can be used for this purpose.
• The if structure has a condition that is either true or false.
• If the condition is true, then a target statement is executed.
• If the condition is false, then the target statement is not executed.
• The condition in if structures can test 2 quantities to see if:
  • they are equal
  • one quantity is less than the other
  • one quantity is less than or equal to the other
• There are 6 such operators in all:

   

  Java	English
  x == y	Is x equal to y ?
  x != y	Is x not equal to y ?
  x < y	Is x less than y ?
  x > y	Is x greater than y ?
  x <= y	Is x less than or equal to y ?
  x >= y	Is x greater than or equal to y ?

• If you embed a space in these operators (e.g., "! ="), it causes a syntax error.
• Reversing the order of the characters that make up an operator (e.g., "=>") causes a syntax error.s