Glossary

A file containing compiled Java byte code. Payroll.class is produced by compiling this lesson’s source file.

A file containing Java source code written by the programmer. Payroll.java is the source file in this lesson.

Describes one parameter in a documentation comment.

Describes the value a method returns; void methods have none.

An escape sequence representing a double quotation mark.

An escape sequence representing one backslash.

An escape sequence representing a newline.

An escape sequence representing a horizontal tab.

True only when both sides are true.

True when at least one side is true.

A keyword that controls where a class or member can be accessed.

A number that identifies a specific location in computer memory.

A well-defined set of steps for solving a problem or completing a task. In our payroll example, the steps are followed in order.

The part of the CPU that performs math and logic operations. ALU stands for Arithmetic and Logic Unit.

An application programming interface; the available classes and methods that let programmers use existing software tools.

A stand-alone program that a person runs to carry out a task, such as calculating payroll.

A program that helps the user complete a particular task.

A value supplied to a method when that method is called.

A value passed in a method call.

A value passed in a method call.

Storing a value in a variable using the = operator.

The operator that stores the value from the right side in the variable on the left. In grossPay = hours * payRate, Java calculates the product and stores it in grossPay.

A piece of data belonging to an object, also commonly called a field in Java.

The smallest unit of computer data. A bit can hold either a 0 or a 1.

Statements grouped by braces { }; the if controls the whole block.

A primitive type with exactly two values, true and false.

The data type that holds only true or false. Every condition produces a boolean value.

Either of the unquoted Java values true or false.

A method that returns true or false.

One of the symbols { and }, used to mark the beginning and end of a body or block.

Ends the switch.

A group of exactly eight bits.

An integer type with values from -128 through 127.

The instructions stored in a compiled Java class file. They are designed for a JVM to execute, rather than for one particular CPU.

A statement that runs a method: its name, parentheses, and a semicolon.

A statement that runs a method: its name, parentheses, and a semicolon.

A naming convention that begins with a lowercase word and capitalizes the first letter of each later word.

An exact compile-time constant to match, such as case 2: or case "Mars":

Treating uppercase and lowercase letters as different characters.

A primitive type that stores one UTF-16 code unit, sufficient for the ordinary single-character examples in this lesson.

A character written between single quotation marks.

A named structure that organizes Java code, including methods and data.

The part of a class declaration that identifies the class and its modifiers before the opening brace.

Writing a task once and calling it wherever it is needed.

A text-based interface where a person types commands for the computer to carry out.

Text in source code that explains the program but does not execute as an instruction.

Returns a negative number, 0, or a positive number depending on alphabetical (Unicode) order.

Software that checks source code and translates it into another form. The javac compiler reports compilation errors and translates valid Java source code into byte code.

A tool that checks Java source code and translates it into bytecode.

A problem reported while a program is being compiled that prevents successful compilation. Syntax errors are one type of compiler error.

Joining values together to form a string.

The + operator when it joins text with another value.

An expression that is either true or false, such as fuel < 25.

The true/false question in the parentheses.

An expression that picks one of two values based on a condition.

A text-based area where a program can display output.

The part of the CPU that directs how instructions are carried out.

The letter at the end of a specifier: d, f, or s.

The part of the computer that processes and carries out instructions. CPU stands for Central Processing Unit.

Restricting direct access to internal data so outside code works through a controlled interface, such as public methods.

A classification that determines which values a variable can hold and which operations are allowed.

A tool that helps a programmer inspect a running program, follow its steps, and find the causes of errors.

Code that introduces a variable by specifying its type and name.

Runs when no case label matches; it is optional.

A storage device that saves information on a spinning magnetic disk.

Breaking a large problem into smaller, easier tasks.

A /** */ comment above a method that describes what it does.

A floating-point type that generally provides about fifteen to sixteen significant decimal digits of precision.

The alternative block of an if-else; it has no condition of its own.

Runs only when the condition before it was false.

An else pairs with the nearest preceding if that does not already have an else.

Combining related data and the methods that work with that data into one unit, such as an object.

Returns true if two Strings contain exactly the same characters.

Compares the characters in two Strings.

Like equals, but uppercase and lowercase count as the same.

A backslash followed by another character that represents a special character inside a literal.

Code that produces a value; it must be used somewhere.

When a case has no break, execution continues into the next case's statements.

The repeated process the CPU uses to get, understand, and carry out instructions.

The minimum number of characters the value takes up.

The minimum number of characters the value takes up.

An option right after %: , groups digits, 0 pads with zeros, - left-aligns.

A boolean variable that records whether a condition was true, such as boolean batteryReady = (battery >= 60);

An option right after %: , groups digits, 0 pads with zeros, - left-aligns.

A floating-point type that generally provides about six to seven significant decimal digits of precision.

A number stored in a format that can represent fractional values and very large or very small magnitudes.

A placeholder starting with % that controls how a value is displayed, such as %.2f.

A placeholder starting with % that controls how one value is displayed.

Breaking a problem into tasks, each done by its own method.

Internal data that outside code is not allowed to read or change directly. In the diagram, outside code uses the object’s methods to work with it.

A method call made from inside another method.

An application that brings programming tools, such as an editor, compiler, and debugger, into one place.

A name used for something in a program, such as a class, method, or variable. The programmer chose the identifiers Payroll, hours, payRate, and grossPay in this example. Some other identifiers come from Java’s existing library.

A name used for something in a program, such as a class, method, or variable. The programmer chose the identifiers Payroll, hours, payRate, and grossPay in this example. Some other identifiers come from Java’s existing library.

A name used to identify something in a program, such as a variable, method, or class.

Runs its block only when its condition is true.

Runs exactly one of two blocks: the if block when the condition is true, the else block when it is false.

Can't be changed once created; a String's text is immutable.

Giving a variable its first value.

Hardware that sends information into a computer.

Hardware used to send information into a computer.

An integer type with values from -2,147,483,648 through 2,147,483,647.

A whole number with no fractional part; it can be negative, zero, or positive.

Software that carries out instructions as a program runs. A JVM can interpret byte code and can also compile some byte code into machine code while running.

A programming language used to write programs. Java source code is commonly compiled into byte code that a Java Virtual Machine executes.

The command used here to start the JVM and run the compiled class. java Payroll uses the class name without the .class extension.

Software that loads and executes Java byte code. Compatible JVMs on different systems allow the same class file to run on those systems.

The command that invokes the Java compiler. javac Payroll.java compiles the source file and produces Payroll.class when compilation succeeds.

The collection of tools used to develop Java programs, including the javac compiler.

A word built into a programming language with a defined meaning. Java reserves these words, so programmers cannot use them as their own names. Examples here include public, class, int, and double.

A word built into a programming language with a defined meaning. Java reserves these words, so programmers cannot use them as their own names. Examples here include public, class, int, and double.

A word Java reserves for a specific purpose in the language.

Places the value at the left of its field width, padding on the right.

How long a variable exists; a local variable lasts for one call of its method.

How long a variable exists; a local variable lasts for one call of its method.

A change in output position that moves subsequent text to a new line.

A value written directly in source code.

A variable declared inside a method or another local block.

A variable declared inside a method or a block.

A variable declared inside a method; only that method can use it.

A mistake that allows a program to run but produces an unintended result.

A mistake in the program’s plan or calculation that causes an incorrect result even though the program can compile and run.

A mistake in the program’s plan or calculation that causes an incorrect result even though the program can compile and run.

An operator that combines or flips boolean expressions: &&, ||, !.

An integer type with a larger range than int.

Temporary working memory that holds programs and information currently being used. It is also called RAM.

The method Java calls to begin executing the programs used in this course.

A named group of instructions associated with a class or object that defines an action or behavior.

A named block of code that performs a particular job.

A named block of statements that runs when it is called.

The code enclosed by the braces that belong to a method.

The statements inside the braces; they run each time the method is called.

Code that asks a method to perform its job.

The part of a method declaration that specifies information such as its name, return type, and parameters.

The first line of a method: modifiers, return type, name, and parameter list.

The first line of a method: modifiers, return type, name, and parameter list.

A keyword such as public or static at the start of a header.

The operator that multiplies its two operands. Here it multiplies hours by payRate.

The ability of an operating system to keep multiple programs running.

Converting a higher-ranked type to a lower one, such as double to int; needs a cast.

Converting a higher-ranked type to a lower one, such as double to int; needs a cast.

An if inside another if; the inner check is reached only when the outer condition is true.

Describes storage that keeps its information when the power turns off.

A software unit that brings related data and the methods that work with that data together. It does not have to represent a physical thing.

An approach to programming that organizes related data and behavior into objects.

A value or expression that an operator works on. In hours * payRate, hours and payRate are the two operands of multiplication.

The main software that manages the computer’s hardware and supports other programs.

A symbol that tells the program to perform an operation on one or more values. In this example, * multiplies and = assigns a value.

A symbol that tells the program to perform an operation on one or more values. In this example, * multiplies and = assigns a value.

A symbol that performs an operation on one or more values.

A storage disc, such as a CD or DVD, that a laser reads.

Information a program produces for a user or another destination.

Hardware that receives information from a computer.

Hardware used to receive information from a computer.

The arrangement of displayed text, including spaces, line breaks, and indentation.

The location where the next character will appear in the console.

A variable in a method header that receives an argument.

The parameters in a header's parentheses, separated by commas.

Passing a copy of an argument's value; the method can't change the caller's variable.

The ability to use a program on different computer systems. Java’s byte code can run on different platforms that have compatible JVMs and the program’s required dependencies.

The order operators are evaluated in; && comes before ||.

Digits after the decimal point.

Digits after the decimal point.

A method that displays a value without automatically adding a line break afterward.

A print method that fills format specifiers with values.

A method that displays a value and then ends the current output line.

An approach to programming that organizes a program around procedures that work with data. In the diagram, the data is separate and passed between procedures.

A named group of instructions that performs a task.

A set of instructions written to tell a computer how to carry out a task.

A set of instructions that tells a computer what to do.

Able to receive different instructions and perform different tasks.

A person who creates, tests, and fixes computer programs.

An identifier that the programmer chooses, rather than a reserved word built into the language. Payroll and grossPay are examples.

A set of words, symbols, and rules used to write instructions for a computer.

An informal description of an algorithm that mixes everyday language with programming ideas. It helps people plan a program and does not have to follow Java’s exact syntax.

An informal description of an algorithm that mixes everyday language with programming ideas. It helps people plan a program and does not have to follow Java’s exact syntax.

An access modifier that allows access from other classes, subject to Java's access rules.

A method that outside code is allowed to call. It can provide controlled access to an object’s hidden data.

Marks that help organize the structure of code, such as semicolons, braces, parentheses, and commas.

Marks that help organize the structure of code, such as semicolons, braces, parentheses, and commas.

A condition that tests whether a value is inside or outside two limits.

Replacing a variable's current value with another compatible value.

The memory location of an object. A String variable stores a reference.

A type whose variables hold references to objects rather than primitive values directly.

A variable that holds the location of an object, such as a String.

An operator that compares two values and produces a boolean: <, <=, >, >=, ==, !=.

A word that Java reserves for language syntax and that cannot be used as an ordinary identifier.

Ends a method and sends a value back to the code that called it.

The type of value a method sends back; void means none.

The type of value a method sends back; void means none.

The type of value a method sends back; void means none.

An error that occurs while a program is executing. If it is not handled, it can interrupt the program or cause it to stop.

An error that occurs while a program is executing. If it is not handled, it can interrupt the program or cause it to stop.

The part of a program where a variable can be used by name.

The part of a program where a variable can be used.

The part of a program where a variable can be used.

A collection of tools for developing software for a particular platform. The JDK is a development kit for Java.

Hardware that keeps programs and files for long-term use.

Hardware that keeps programs and files for long-term use.

The value in switch ( ) that is compared to each case label.

The ; symbol that marks the end of many Java statements.

A punctuation mark that ends many Java statements, including the assignments and print statement in Payroll.java. Class headers and braces do not need an ending semicolon.

An integer type with values from -32,768 through 32,767.

Java stops evaluating as soon as the result is known.

Java stops evaluating a && or || expression as soon as the result is known.

The digits that contribute to a number's precision, counted across the number rather than only after its decimal point.

Each method has one clear job.

Each method has one clear job.

Programs and instructions that tell a computer what to do.

An organized approach to designing, building, testing, and maintaining software, often involving a team and a larger project.

A storage device that uses electronic memory and has no moving parts. It is often shortened to SSD.

The program text a programmer writes in a programming language. The Java source code in this lesson is saved in Payroll.java.

The instructions a programmer writes in a programming language, such as Java.

Two or more labels with no statements between them share the same body.

A unit of code that tells the program to perform an action. The assignment on line 8 is one statement. This statement ends with a semicolon.

An instruction that Java executes.

A modifier that allows a method to be called without first creating an object of its class.

The information a variable currently holds.

A Java reference type used to represent text.

Text written directly in code between double quotation marks.

Builds formatted text and returns it as a String instead of printing it.

A method that returns the characters from start up to, but not including, end.

The rules for arranging the words and symbols of a programming language into valid code. For example, the assignment statement on line 8 must end with a semicolon.

The rules that describe how valid Java code must be written.

A mistake that breaks the language’s rules for writing code, such as a missing required semicolon or closing brace. The compiler reports it before the compiled program can run.

A mistake in the structure of code that prevents it from being accepted as valid Java.

Java's standard output stream, used here to send text to the console.

Input values chosen to check whether a program behaves as expected.

throws IOException in a header: this method may fail while reading a file.

throws IOException in a header: this method may fail while reading a file.

Dividing the CPU’s attention among multiple running programs.

Following a program's instructions in order to determine what happens.

A local variable that has been declared but has not yet been assigned a value.

A small, portable storage device that connects to a USB port.

Checking that a program’s actual results are correct and meet the intended goal, rather than checking only that the program runs.

A method that sends a value back to the code that called it.

A method that sends a value back to the code that called it.

A method that sends a value back to the code that called it.

A named storage location that holds a value the program can use or change. Think of it as a labeled box that holds one value at a time.

A named storage location that holds a value.

A return type indicating that a method does not return a value to its caller.

A method that does a task and sends no value back.

Describes memory that loses its information when the power turns off.

Converting a lower-ranked type to a higher one, such as byte to int; automatic.