1.7. Unit 1 Summary

In this unit you learned about the three primitive data types on the exam: int, double, and boolean. You also learned how to declare (name) and change the value of variables. You learned about operators, casting, and integer constants for the min and max integer values.

1.7.1. Concept Summary

  • Compiler - Software that translates the Java source code (ends in .java) into the Java class file (ends in .class).

  • Compile time error - An error that is found during the compilation. These are also called syntax errors.

  • Main Method - Where execution starts in a Java program.

  • Boolean - An expression that is either true or false.

  • Camel Case - One way to create a variable name by appending several words together and uppercasing the first letter of each word after the first word (myScore).

  • Casting a Variable - Changing the type of a variable using (type) name.

  • Double - A type in Java that is used to represent decimal values like -2.5 and 323.203.

  • Declare a Variable - Specifying the type and name for a variable. This sets aside memory for a variable of that type and associates the name with that memory location.

  • Initializing a Variable - The first time you set the value of a variable.

  • Integer - A whole number like -32 or 6323.

  • modulo - The % operator which returns the remainder from one number divide by another.

  • Operator - Common mathematical symbols such as + for addition and * for multiplication.

  • Random Number - A random number picked from a range of numbers. Used in games to make the game more interesting.

  • Shortcut Operators - Operators like x++ which means x = x + 1 or x *=y which means x = x * y.

  • Variable - A name associated with a memory location in the computer.

1.7.2. Java Keyword Summary

  • boolean - used to declare a variable that can only have the value true or false.

  • double - used to declare a variable of type double (a decimal number like 3.25).

  • false - one possible value for a boolean variable.

  • int - used to declare a variable of type integer (a whole number like -3 or 235).

  • static - means that the field or method exists in the object that defines the class.

  • true - one possible value for a boolean variable.

1.7.3. Vocabulary Practice

    1-7-1: Drag the definition from the left and drop it on the correct concept on the right. Click the "Check Me" button to see if you are correct Review the summaries above.
  • Specifying the type and name for a variable
  • declaring a variable
  • A whole number
  • integer
  • A name associated with a memory location.
  • variable
  • An expression that is either true or false
  • Boolean
    1-7-2: Drag the definition from the left and drop it on the correct concept on the right. Click the "Check Me" button to see if you are correct. Review the summaries above.
  • Setting the value of a variable the first time
  • initialize
  • An operator that returns the remainder
  • mod
  • a type used to represent decimal values
  • double
  • changing the type of a variable
  • casting

1.7.4. Common Mistakes

  • forgetting that Java is case sensitive - myScore is not the same as myscore.

  • forgetting to specify the type when declaring a variable (using name = value; instead of type name = value;)

  • using a variable name, but never declaring the variable.

  • using the wrong name for the variable. For example calling it studentTotal when you declare it, but later calling it total.

  • using the wrong type for a variable. Don’t forget that using integer types in calculations will give an integer result. So either cast one integer value to double or use a double variable if you want the fractional part (the part after the decimal point).

  • using == to compare double values. Remember that double values are often an approximation. You might want to test if the absolute value of the difference between the two values is less than some amount instead.

  • assuming that some value like 0 will be smaller than other int values. Remember that int values can be negative as well. If you want to set a value to the smallest possible int values use Integer.MIN_VALUE.

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