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CS21, Java -Chapter 1 Quiz –MCTF

Know the definitions of the following:

•Compiler

•Bytecode

•Console Window

•Syntax Error

•Logic Error

•Runtime Error

Know the rules that apply to string literals

Know if the name of a Java file and the name of a Java class have to be the same

Know if methods other than main are allowed to call other methods

Know where the flow of control goes when a method finishes executing

Know what data is contained in files with extensions .java and .class

Know what characters are allowed as the first character of an identifier

Know all escape sequences

Know what the following keywords mean:

•public

•static

•void

•main

Know what symbols are used for each of the following:

•Contain methods within a class

•Contain code within a method

•Terminate a line of code

•Contain a string literal

•Indicate single-line comments

•Contain multiple-line comments

Answer 1

Compiler

Basically compilers are used just like translators. In JAVA the compiler takes the source file and convert it into a platform independent JAVA file. The output of the compiler is a JAVA class file which having JAVA bytecodes.

ByteCodes

          In a single line we can define the bytecode as the instruction set of the Java Virtual Machine. For JAVA bytecode act like an assembler. It gets generated after compilation. In other words we can also define bytecode as the machine codes in the form of (.class) file. These are platform independent codes.

Console Window

          Console window is a platform or area that you get when executing the command cmd.exe on run. By using console window we can compile and execute the java programs.

Syntax Error

          These errors occurs due to avoidance of syntax, while writing the statements or functions in a program. When syntax error occurs then we will be unable to execute the program.

Logical Error.

          These errors will not stop execution of a program. These will result wrong or unexpected output or may lead to infinite loop(If any logical error occur in loops). These cannot be identified by compiler or JVM.

Runtime Error

          As the name suggests these errors occur during the execution time. These errors can not be detected by compiler rather JVM can detect. These are also called as Exceptions.

Rules Applied to String Literals

          The string literals always enclosed within double quotation marks. In JAVA strings can also be represented by using Unicode characters.

Know if the name of a Java file and the name of a Java class have to be the same

        In JAVA the class name and file name must be same if the class is public. It provides the path to JVM as an entry point to execute the program. Because in a program we may use number of classes which may leads to confusion. If the class is not public then we may use different file name.

Know if methods other than main are allowed to call other methods.

          If methods other than main are allowed to call other methods then the method in which other methods are called, it must be called inside the main() method.

Know where the flow of control goes when a method finishes executing

          After execution of a method the control will move to the block from where the method was called.

Know what data is contained in files with extensions .java and .class

The .JAVA file consists of the source code that the programmer have written but the .class file consists of the bytecodes.

Know what characters are allowed as the first character of an identifier

All the alphabets as a…z or A…Z

Underscore is allowed as a first character.

Digits are not allowed as first character.

Know all escape sequences

          Escape sequences are preceeded by backslash(\) and having a specific meaning. Certain non printable characters can be printed by using escape sequences.

\t	Inserts a tab.
\b	Inserts a backspace.
\n	Inserts a newline .
\r	Inserts a carriage return.
\f	Inserts a form feed
\'	Inserts a single quote .
\"	Inserts a double quote character .
\\	Inserts a backslash character

Meaning of

Public: It is an access specifier. It allows the methods or members to access globally. In JAVA main() is declared as public because JVM can access it from outside the class as it is not present in the current class.

Static:

            Static keyword makes a method as a class related method.The main() method is static so that JVM can invoke it without instantiating the class.

Void

This keyword is used when a method does not return any thing. It is basically used in main() method since it will not return anything.

Main

“main” is not a keyword. It is the name of Java main method. It is the identifier that the JVM will start the execution from this.

Symbols used

Contain methods within a class

A pair of curly braces {} are used to provide the methods with in a class after the name of class.

Contain code within a method

A pair of curly braces {} are used to provide the codes within a method after the name of method with return type and arguments(if any).

Terminate a line of code

Semicolon(;) is used to terminate a line of code.

Contain a string literal

Double quotation symbol is used for string literals

Indicate single-line comments

// is used for single line of comments

Contain multiple-line comments

/* comments*/ is used for multiple line comments.