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What are the reserved literals?
null, true, false
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What are the reserved keywords not in use?
const, goto
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What are the integer data types?
int, long, byte, short
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What must identifiers start with?
letter, $, _ or other connector
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What can identifiers NOT start with?
a number
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What is the max length of a Java identifier?
There is no limit
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Are Java identifiers case sensitive?
Yes
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What can a Java identifier contain after the first character?
any combination of letters, currency characters, connecting characters, or numbers
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Legal or illegal identifier: .f
illegal cannot start with a .
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Legal or illegal identifier: _$szygy
legal
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Standard for naming Classes and Interfaces
CamelCase (i.e. MyGreatJavaClass)
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Standard for naming Methods
first letter lowercase, remainder CamelCase (i.e. myMethodActing)
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Standard for naming variables
first letter lowercase, remainder CamelCase (i.e. myMethodActing)
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Standard for naming constants
UPPERCASE with _ as a separator (i.e. MIN_HEIGHT)
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The name of a Java class file...
must match the name of the public class if there is one
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A Java file with no public classes can have what type of name?
It can have any legal name
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Class Access modifiers
public, protected, private - default access has no modifier
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What are the nonaccess class modifiers?
strictfp, final, abstract
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A subclass inheriting a member is exactly the same as...
The subclass declaring the member itself
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How many public classes can be in a source file?
Exactly one
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Where must the package statement be for classes in a package?
On the first line, before any import statements
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Where must import statements go?
Between the package statement and any class declarations
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Where must a class declaration go when there are no package or import statements?
It must be the first line of a source file
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When can an abstract class be instantiated?
Never
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What is the purpose of an abstract class?
To be extended (subclassed)
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What does final mean when applied to a class?
A final class can't be subclassed
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All interfaces are implicitly, what?
public and abstract
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All variables defined in an interface must be what?
public, static, and final (i.e. constants)
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Interface methods are 100% abstract
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What are the member access control levels?
Public, Protected, default (if nothing specified), private
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What must a class be declared as, to have an abstract method?
The class must be declared as abstract
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A method cannot be both Abstract and ...?
Abstract and Final, Abstract and Private
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Synchronized method keyword means
Method can only be accessed by one thread at a time
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"native" means
That the method is implemented in platform-dependent code
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"native" can only be applied to what?
methods - not classes or variables
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strictfp can modify
a class or method declaration
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strictfp means
enforce IEEE754 standard
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What are var-args?
methods that take a variable number of arguments
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How is a var-arg declared?
datatype followed by ... followed by the arg name
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Which is legal: var test(int ... x) or var test(int ...)
var test(int ... x)
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How many var-args can be in a method?
One
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Where must the var-arg be in the parameter list?
at the end
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What can't a constructor have?
a return type
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How are constructors different from methods?
Constructors don't have a return type
- What are the eight primitive types?
- char, boolean, short, double, float, byte, int, long
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a reference variable is used to
refer to or access an object
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A byte datatype takes x bytes and y bits
1 byte, 8 bits
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A short datatype takes x bytes and y bits
2 bytes, 16 bits
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An int datatype takes x bytes and y bits
4 bytes, 32 bits
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A long datatype takes x bytes and y bits
8 bytes, 64 bits
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A float datatype takes x bytes and y bits
4 bytes, 32 bits
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A double datatype takes x bytes and y bits
8 bytes, 64 bits
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What is the range of byte, short, int, long?
(-2) ^ (bits -1) to (2 ^ (bits -1))-1
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Instance variables are defined
inside the class, but outside any method
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Which access levels can Instance variables use
any of the 4 access levels
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What keyword can be used to resolve name collisions?
this
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Is the statement int [5] scores; legal? If not, why?
No, cannot include the size of the array in the declaration
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What keyword tells Java to skip an instance variable when serializing?
transient
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What other keyword can only be applied to instance variables?
volatile
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What keyword identifies a variable as shared by all instances of a class containing that variable?
variable
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What things CAN be marked as static?
methods, variables, initialization blocks, a class nested in another class but not within a method
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What things CAN'T be marked as static?
Constructors, classes (unless nested), Interfaces, Method Local Inner Classes, Inner Class methods and instance variables, local variables
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Where CAN'T an enum be declared?
Within a method
- What are the escape characters?
- Big Farms Need Red Tractors - \b backspace, \f formfeed, \n newline \r carriage return \t horizontal tab \' single quote \" double quote \\ backslash
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