CMPUT101 Lecture Notes - Lecture 4: Dollar Sign

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erinpug668

16 Nov 2011

School

University of Alberta

Department

Computing Science

Course

CMPUT101

Professor

Duane Szafron

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Document Summary

Cmput 114 lecture 4 references: literals, variables and. In a written program, we can"t draw shapes so we need to have some notation for referring to objects and values called a reference. There are different ways to reference objects & values in a. The simplest way is to use a literal in our code. A literal refers to the same object or value at all times. You can think of a literal as a nameplate that is automatically pre-bound to an object or value. In general, a literal is recognized by the compiler and is immediately translated into a language value or object. Common literals in programming languages include characters, numbers, and strings. Some objects cannot be referred to using literals. Sometimes we may want to rebind our nameplates. A variable is like a soft nameplate that may be attached to an object or value and may be re-attached to a different object or value in the future.

Related Questions

2. In this section you will be shown several classes. Inside the code for each class will be a question. You should provide your answer to the question inside the chart. Many of the questions will ask you whether a variable has changed or not. In cases that the variable being asked about is a primitive type, you should provide your answer based on the data stored in the primitive type. In cases that the variable being asked about is a reference type, you should provide your answer based on the data stored at the Object linked to by the reference type. For example, in the first snippet, the question asks about the variable x defined in the main method. Since x is a primitive type, you should answer YES if you think the variable x has had its value changed after the method methodOne() returns. All your answers should go in the chart below: (9 points) Part Answer to question x changed (circle one)? YES NO y changed (circle one)? a changed (circle one)? b changed (circle one)? d1 a changed (circle one)? b changed (circle one)? YES e words changed (circle one)? YES NO Values in array of array referred to by y: What is printed to the screen? (a) public class ReferenceTesti public static void methodOne (int x){ x++; public static void main(String[args) { int x = 0; methodOne (x); //IS THE DATA STORED OR REFERRED TO BY X THE SAME? (ANSWER IN CHART)

2)What code would you add if you wanted to change it so that the user was able to continue entering a filename until the method initialize InventoryFromFile could successfully be exceuted? (e) Suppose I have the following class definition: 1 1/A TelevisionShow is a new type that consists of a String) for the actors |/ /a String for the name, and a string for the network public class Television Show private String[] actors; private String name; private String network; //this method will return whether or not the property //actors contains actor Name or not public static boolean hasActor (String actor Name) for (int i-0; i < actors.length; i++) { if (actors[i].equals (actorName)) { return true; return false; Unfortunately, when I try to compile this code, I get the following error: Television Show.java:11: non-static variable actors cannot be referenced from a static context for (int i=0; i < actors.length; i++) { Television Show.java:12: non-static variable actors cannot be referenced from a static context if (actors[i].equals(actorName)) { 2 errors What does this error mean and how can I fix it?

Type of Errors For each of the following answer whether they would cause an compiler error, runtime error, or a bug. In other cases the mentioned error may not cause a problem for the computer and is merely a question of style. In this case you should choose "Style" In other cases the question may not cause a problem at all in which case you should answer "No Error" For the purpose of this question, you can use the following definitions: • Compiler error : An error that occurs during the compilation phase of your development. In this case no class file is produced. • Runtime error: An error that occurs while you are running your program. Your program starts to execute but terminates before the main method has finished executing. • Logical error or bug : An error that results in the wrong results being seen • Style error: The error does not make a difference to the computer but is something that may be considered bad code. 7. Omitting a semi-colon at the end of a variable assignment. (A) Compiler Error (B) Bug (logical) Error (C) Style (D) Runtime Error (E) No Error

CMPUT101 Lecture Notes - Lecture 4: Dollar Sign

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