Term
Which keyword is not implmeneted in java because its harmful?
a. abstract
b. goto
c. transient |
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Instance of using const, for a constant which key word do we use?
a.static
b.final
c.private |
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Why is this illegal ?
public int break(int b) { }
public int switch(int b) {} |
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Definition
| break and switch are reserved key words |
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Why is this illegal ?
public int break(int b) { }
public int switch(int b) {} |
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Definition
| break and switch are reserved key words |
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Term
A char is a unicode char.. how many bits.
8,16,32,64? |
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a double is a 64 bit flopating point
is it signed or unsigned? |
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| A flat is a ___ bit floating point number |
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| a long is a _____ bit ______ integer |
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| an int is a a 32 bit SIGNED or UNSIGNED ? |
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Both short and byte are SIGNED integers.
How many bit does a short have? |
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Both short and byte are SIGNED integers.
How many bit does a bye have? |
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From broadest to the narrowest which is the correct order?
double float, long, int, byte, short
double, float, int, long, byte,short
double, long, flat, short, int , byte
double, float, long,int, short, byte |
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Definition
| double, float, long,int, short, byte |
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Term
| Float f = 23.23568 fails, why? |
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Definition
Float f = 23.23568F (needs to be attached) because a FP literal
is deinfed a s a double (64 bits), not with 32 bits |
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Term
Why is this illegal?
int x = 1; if (x) { } |
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Definition
| Because x is not "true" or "false" |
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Term
Char literals can also be represented as an integer, as long as it’s less than
1. 65536
2. 65537
3. 65538 |
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This deinfes what kind of character?
char c = ‘\”’;
1. double quote
2. single quote |
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Is this legal?
char b = 982; |
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Definition
| Yes because its an int literal |
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Term
Is this legal?
char c = 70000; |
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Definition
No, out of range, less than 65536, to make legal use cast
char c = (char) 70000 |
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Is this legal?
char c = -29 |
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Definition
| No , possible of loss of precision, need a cast, char is unsigned. |
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Term
Delcare an array Two ways: before or after name
a) int [ ] key;
b) int key [ ] ;
which is recommended (a) or (b)? |
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Is this legal?
int[5] scores; |
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Definition
| No, never legal to include the size of array in declaration |
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Declare, construct, and assign this in one line.
TEST SCORES array of ints size of 4. |
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Definition
| int [] testScores = new int[4]; |
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Definition
| No because arrays must always be given a size at the time they are constructed. |
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Term
Multidimensional Arrays - are these legal?
1. int [ ] [ ] ratings =
new int [3] [ ];
2. scores [0] = new int [4];
3. scores [1] = new int [6];
4. scores [2] = new int [1]; |
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Term
How do you intilize array of dots
in one line as a list. |
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Is this legal?
Dog puppy = new Dog(“Frodo”);
Dogs[] myDogs = {puppy, new Dog (“Clover”), new Dog(“Aiko”)}; |
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Definition
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Term
int [ ] [ ] scores = { {5,2,4,7}, {9,2}, {3,4} };
scores [0] // holds this array {5,2,4,7}
scores [2] //holds this array {3,4}
scores[2][1] //Accesses which value? |
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Legal?
int [] scores;
scores = new int[] {4,7,2}; |
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Definition
YES
/used for just in time array |
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Term
| scores = new int[3] {4,7,2} //legal? |
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Definition
| scores = new int[3] {4,7,2} //legal? NO – do not put size. |
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Term
An array has a ____ relationship.
class Car{}, class Honda extends Car{}
i.e. Car [ ] my Cars = { new Honda() };
a. IS-A
b. HAS-A |
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Definition
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Term
int[] splats;
int [] dats = new int[4];
char[] letters = new char[5];
splats = dats; // legal? |
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Definition
| Ok, dats refer to an int array |
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Term
int[] splats;
int [] dats = new int[4];
char[] letters = new char[5];
splats = letters //legal? |
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Definition
| NO, letters refer to a char array |
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Term
• int[ ] [ ] books new int [3] [];
• int [ ] numbers = new int[6];
• int aNumber = 7;
• books[0] = aNumber // Compile? |
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Definition
| No , expect an int array instead of int |
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Term
• int[ ] [ ] books new int [3] [];
• int [ ] numbers = new int[6];
• int aNumber = 7;
• books[0] = numbers // |
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Definition
| Compile? Yes, numbers is an int array. |
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Term
default value for char is
a.‘\u0000’
b. 0 |
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Definition
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Term
When an array of objects is instantiated, objects within the array are instantiated automatically.
T or f? |
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Definition
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• When an array of primitives is instantiated, all elements get their default values
T or F |
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Definition
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• Just as with array elements, instance variables are always initialized with a default value.
T or F |
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Definition
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Term
| • Local/automatic/method variables are always given a default value. If you attempt to use one before initializing it, it will compile but Instance Variables are T or F |
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Term
//Local objects and arrays
Date d ;
if (d == null){
System.out.println(“date is null”);
}
Why will this crash? |
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Definition
| //Will crash because you have to explicitly set d to null. A null references Is not the same as an uninitalized reference! |
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Term
• The first command-line argument is the first element in the main String array parameter.
%java TestMain Hello
//First arg is ____ |
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Definition
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Term
| • If no arguments are passed to main, the length of the main String array parameter will be ____ |
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Definition
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Term
HOw many public class per source code.
1. 0
2. 1
3. 2 |
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Definition
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These classes are default, can this compile and why?
i.e. package cert; package exam.stuff
___class Bev{ } import cert.Bev;
____class Tea extend Bev { //can’ |
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Definition
| No because thtey are both in DIFFERENT packages. We can make one of the classes public to make it compile |
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Term
strictfp can modify which of the following
class
method
variable |
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Definition
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Term
| Is this legal abstract strictfp class Blah? |
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Definition
| Yes because strictfp applies to classes or methods. |
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Term
Is this legal?
final stricttfp class |
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Definition
| Yes because strictfp applies to classes or methods |
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Term
| public final class ? Is this legal? |
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Definition
| Yes because of inheritance |
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Term
Is this legal?
final abstract class |
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Definition
| NO, a class can never be FINAL AND ABSTRACT. contradiction abstract(has to be extended), final can’t |
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Term
Final class :
1.can’t be subclassed,
2.no class can extend a final class.
which is true? |
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Definition
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Abstract class MKUST BE
1. Instantiated
2. Extended (sublcasses)
3. BOTH |
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Definition
| 2. Absturact classes can ONLY be extended NEVER instantiated |
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Term
Will this compile?
abstract class Car{
private double price;
public abstract void goFast();
} |
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Definition
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Term
class Honda extends Car { implement methods here }
Which is the parent abstract class? |
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Definition
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Term
Do rules of overriding apply for private methods
i.e. private void jump()
public void jump() |
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Default Members (Package restrictions)
- can be accessed only if the class accessing the member belongs to the ____ package.
a. different
b. SAME |
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Definition
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Term
package cert;
public class Parent {
int x = 9 ;//default
}
package different;
class Child extends Parent{
public void testIt(){
System.out.println(x); // cam we ise this “x”.
}
} |
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Definition
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Term
package cert;
public class Parent {
int x = 9 ;//default
}
package cert;
class Child extends Parent{
public void testIt(){
System.out.println(x); // compiles?
}
} |
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Definition
| yes because its in the same package |
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Term
Protected Keyword (used for inheritance) [Packaged kids]:
used to define a member, any subclass of the class declaring the member can access it regardless if they are different packages. The subclass can only see the protected member through inheritance |
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Definition
| YES because of inheritance |
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Term
Protected Keyword (used for inheritance) [Packaged kids]:
used to define a member, any subclass of the class declaring the member can access it regardless if they are different packages. The subclass can only see the protected member through inheritance |
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Definition
Compiler error, trying to access it
through parent reference! |
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Term
Local variables only have___ access
public int x = 7
protected int x = 7
final int x = 7
static int x = 7 |
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Definition
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Abstract Methods: declared but not implemented, required to be ________
a. extended
b. declared |
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Definition
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Term
public abstract class A{
abstract void foo();
}
class B extends A{
void foo(int I){ //will this line compile?
}
} |
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Definition
| won’t compile this is overloaded! |
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Term
| abstract final Method? legal? |
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Definition
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abstract synchronized, strictfp, native void thisMethod(); ?
lega? |
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Definition
| NO explains implemenation detils... |
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Term
abstract static doStuff();
Is this legal? |
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Definition
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Term
Synchronized – only applies to ______, can be accessed only one thread at a time.
classses
methods |
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Definition
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public/private/default/protected synchronized method ?
legal? |
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Definition
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synchronized final method?
compiles |
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Definition
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Term
synchronized final class?
compiles? |
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Definition
| NO because synchronized only applies to methods |
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Term
Native used only for ____implemented in a platform independent way,
never combined with abstract.
classes or methods? |
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Definition
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Term
| Strictfp => used for both Classes and what kind of methods: |
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Definition
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Term
For instance variables
what are the 3 legal types? |
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Definition
| final, transietn, volatire |
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Term
For instance variables, what
is illegal? (4) |
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Definition
| abstract, syyncrhoized, strictfp, natvie |
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Term
| final instance variables need to be intilized by the time the _______ method appears. |
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Definition
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Term
| Do local variables get default values? |
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Definition
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Term
For objects, can be modified, but reference variable (bit pattern can’t be changed).
final Date d = new Date();
d.setYear(2001) //compiles
d = new Date (); //can’t compile why not? |
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Definition
| because we’re changing the bit pattern. (ref variable) |
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Term
What does this print
i.e. class Frog{
static int frogCount = 0;
public Frog() {
frogCount +=1;
}
public static void main (String [] args){
new Frog();
new Frog();
System.out.println(frogCo |
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Definition
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Term
Source File Structure:
package com.geeks;
import java.util.* //wild card package import
import com.wicketlysmart.Foo; //Explicit class import.
WIll these compile |
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Definition
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Term
Why these not compile?
import java.util.ArrayList.*
import java.util; |
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Definition
import java.util.ArrayList.* => won’t compile because it is a class not package.
import java.util; //won’t compile since util is not a class. |
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Term
| static void b(); //compile? |
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Definition
| illegal, defines instance methods |
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