Term
| What can valid identifiers begin with? |
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Definition
| Letter, underscore or currently symbol. |
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Term
| What is the maximum length of an identifier. |
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Definition
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Term
| JavaBeans must be named using _______ and depending on the methods purpose must start with ___, ___, __, ___, or ______. |
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Definition
| JavaBeans must be named using camelCase and depending on the methods purpose must start with get, set, is, add, or remove. |
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Term
| How many public classes can a source file have? |
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Definition
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Term
| How many package statements are allowed and where must they be? |
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Definition
| Only one is allowed and it must be the first statement in the file. |
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Term
| Where must the import statement go? |
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Definition
| At the begining of the file AFTER the package statement (if present) otherwise it must be the first statement in the file. |
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Term
| How many public classes can be in a source file? |
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Definition
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Term
| True/False there can be only one top level class. |
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Definition
| False, you can have many top level classes, but only one Public class. |
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Term
| True/False When a thread is sleeping it releases its locks. |
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Definition
| False, Locks are only released on wait() |
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Term
| What access modifiers can interfaces have for declarations? |
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Definition
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Term
Will This Compile?
interface Arachnid{ void bite();}
public class BlackWidow implements Arachnid{
void bite();}
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Definition
| No, the interfaces are declared as public whether they say so or not. The class then changes it to default (package) access. It will not compile. |
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Term
What is the output?
int k=8;
int s=0;
for(int i=5;i>2;i--){
s=k-i;
break;
}
System.out.println(s);
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Definition
S would be 3.
It's easy to think that S might be 4 instead abut the postfix operator doesnt occur until AFTER the code block has executed. |
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Term
What is the result of compilation?
class Fuel{
static int getFuel(){return 23}
}
class Gas extends Fuel{
public static void main(String[] args){
System.out.println(super.getFuel());
}
}
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Definition
Compilation fails.
Only instance methods can be overridden. Calls to super only apply to overridden methods. |
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Term
Will this compile?
List<Number> numbers = new ArrayList<Integer>(); |
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Definition
| No, Interger is a subtype of Number. |
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Term
Will this compile?
List<JButton> numbers = new ArrayList<JButton>(); |
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Definition
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Term
| What will accept?
1. Animal
2. Dog
3. Mammal
4. Cat |
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Definition
Animal, Dog, Cat
Since Mammal does not extend from Animal and is a supertype of Animal it will fail type checking. |
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Term
| What will accept?
1. Animal
2. Dog
3. Mammal
4. Cat |
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Definition
Animal, Mammal, Dog
Since Cat is not a supertpe of Dog it will fail type checking. |
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Term
Will this compile?
1) List list = new ArrayList();
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Definition
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Term
Will this compile?
2) List aList = new ArrayList();
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Definition
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Term
Will this compile?
3) List foo = new ArrayList(); |
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Definition
No.
Problem: you cannot use wildcard notation in the object creation. So the
new ArrayList() will not compile. |
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Term
Will this compile?
4) List cList = new ArrayList(); |
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Definition
No
Problem: You cannot assign an Integer list to a reference that takes only a
Dog (including any subtypes of Dog, of course). |
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Term
Will this compile?
5) List bList = new ArrayList();
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Definition
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Term
Will this compile?
6) List dList = new ArrayList();
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Definition
| No
Problem: You cannot assign a Dog to . The Dog is too "low"
in the class hierarchy. Only or |
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Term
Will this compile?
public class NumberHolder{} |
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Definition
No.
The ? will not work for generic class and method declarations. |
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Term
Will this compile?
public static List backwards(List input) |
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Definition
No.
You cant use wildcards in the type variable declaration. |
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Term
Will this compile?
public static List backwards(List input) |
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Definition
No
You can not use wildcards in the type variable declaration. |
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Term
Will this compile?
public static List backwards(List input) |
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Definition
Yes.
You can define the type passed to a declaration with the ? wildcard parameter. |
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Term
Is this statement true?
If the equals() method returns true, the hashCode() comparison == might return false. |
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Definition
No, This is a negation of the hashCode() and equals() contract. (Objective 6.2)
x.equals(y) == true then x.hasCode() == y.hashCode() (REQUIRED) |
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Term
Is this statement true?
If the hashCode() comparison != returns true, the equals() method might return true. |
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Definition
No, This is a negation of the hashCode() and equals() contract. (Objective 6.2)
x.hasCode() != y.hashCode() then x.equals(y) == false (REQUIRED) |
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Term
Is this statement true?
If the equals() method returns false, the hashCode() comparison == might return true. |
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Definition
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Term
Is this statement True?
If the hashCode() comparison == returns true, the equals() method might return true. |
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Definition
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Term
What is the result?
String s="Pod";
s.substring(1,7);
s.insert(0,"i");
System.out.println(s);
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Definition
| Compilation fails. Strings do not have an insert method. |
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Term
| The HashMap uses what methods for inserting and retreiving data? |
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Definition
| put(K key, V value) and get(Object key) |
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Term
| The LinkedList uses what methods for inserting and retreving data? |
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Definition
add(E o)
Appends the specified element to the end of this list
add(int index, E element)
Inserts the specified element at the specified position in this list.
get(int index) |
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Term
Will this compile?
short [][]b = new short[4][4];
short b3=8;
b[1][0]=b3;
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Definition
Yes
A short fits into the arra element directly. |
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Term
Will this compile?
short [][]b = new short[4][4];
short b2[][][][] = new short[2][3][2][2];
b2[1][1][0][1]=b1[1][0];
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Definition
| Yes because your assigning a value from the 2 dimension b1 to the single demsion item in b2. |
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Term
What is the result?
int x=0;
for(int y=2;y>0;y--){
x++;
}
System.out.println(x+y);
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Definition
Compillation fails.
y is out of scope. |
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Term
What is the result?
int x=2;
int y;
for(y=2;y>0;y--){
x++;
}
System.out.println(x+y);
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Definition
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Term
Scope1.java Contains:
class ForNext{
public static void main(String arg[]){
int y; for(y=2;y>0;y--){System.out.println(x+y);}
}
What happens when you run it with "java Scope1" |
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Definition
Exception in thread "main" java.lang.NoClassDefFoundError: Scope1
This is because the compiler creates a ForNext.class |
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Term
Will this compile?
throw new RuntimeException(); |
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Definition
| yes, you can throw a new RuntimeException(); |
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Term
| What calls will request the Garbage Collector to run? |
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Definition
System.gc()
and
Runtime.getRuntime().gc() |
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Term
What is the result?
class crap{
public void static main(String[] args){poo();}
static void poo(){System.out.println("hi");
{System.out.println("bye");}
} |
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Definition
Just "Hi"
The {} init block is never called because the constructor was never called. The static method doesnt require the constructor. |
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Term
What is the result?
class myNum{
public void static main(String[] x){
int i;
System.out.printlin(go(i));
}
int go(int z){return ++z;}
}
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Definition
Compilation fails.
go (instance method) is being called from a static method |
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Term
True or False
protected is less restrictive that default |
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Definition
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Term
True/False
Protected member can be accessed by a subclass regardless of the package it's in. |
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Definition
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Term
| What are the access levels for a class in order from less restrictive to most restrictive? |
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Definition
Public
Protected
Default
Private |
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Term
Which of the following can be used in a switch or case statement?
byte
char
int
short
long
double |
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Definition
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Term
| In regex what does \w search for |
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Definition
| Word characters (Digits, letters or seperators) |
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Term
| What is the ^ operator for? |
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Definition
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