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Do rules of overriding apply for private methodsi.e. private void jump() public void jump()
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No it does not
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Final class : 1.can’t be subclassed, 2.no class can extend a final class.which is true?
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both statements are
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Float f = 23.23568 fails, why?
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Float f = 23.23568F (needs to be attached) because a FP literalis deinfed a s a double (64 bits), not with 32 bits
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Source File Structure:package com.geeks;import java.util.* //wild card package importimport com.wicketlysmart.Foo; //Explicit class import.WIll these compile
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YES
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Why these not compile?import java.util.ArrayList.* import java.util;
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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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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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No because thtey are both in DIFFERENT packages. We can make one of the classes public to make it compile
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static void b(); //compile?
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illegal, defines instance methods
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• int[ ] [ ] books new int [3] [];• int [ ] numbers = new int[6];• int aNumber = 7;• books[0] = aNumber // Compile?
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No , expect an int array instead of int
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HOw many public class per source code.1. 02. 13. 2
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1
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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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T
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Delcare an array Two ways: before or after namea) int [ ] key;b) int key [ ] ;which is recommended (a) or (b)?
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a
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abstract static doStuff();Is this legal?
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NO
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For objects, can be modified, but reference variable (bit pattern can’t be changed). final Date d = new Date();d.setYear(2001) //compilesd = new Date (); //can’t compile why not?
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because we’re changing the bit pattern. (ref variable)
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Local variables only have___ access public int x = 7protected int x = 7final int x = 7static int x = 7
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final int x = 7
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int[] splats;int [] dats = new int[4];char[] letters = new char[5];splats = letters //legal?
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NO, letters refer to a char array
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final instance variables need to be intilized by the time the _______ method appears.
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constructor
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synchronized final method?compiles
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YES
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For instance variableswhat are the 3 legal types?
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final, transietn, volatire
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Do local variables get default values?
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NO
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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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YES because of inheritance
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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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Yes
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A flat is a ___ bit floating point number
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32
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Default Members (Package restrictions)- can be accessed only if the class accessing the member belongs to the ____ package.a. differentb. SAME
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SAME
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Declare, construct, and assign this in one line.TEST SCORES array of ints size of 4.
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int [] testScores = new int[4];
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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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4 [{3,4}]
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Char literals can also be represented as an integer, as long as it’s less than 1. 655362. 655373. 65538
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1. 65536
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int[] splats;int [] dats = new int[4];char[] letters = new char[5];splats = dats; // legal?
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Ok, dats refer to an int array
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abstract synchronized, strictfp, native void thisMethod(); ?lega?
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NO explains implemenation detils...
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Synchronized – only applies to ______, can be accessed only one thread at a time.classsesmethods
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methods
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abstract final Method? legal?
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No, contradicts
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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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Compiler error, trying to access it through parent reference!
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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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yes
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default value for char is a.‘\u0000’b. 0
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a.‘\u0000’
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Native used only for ____implemented in a platform independent way,never combined with abstract.classes or methods?
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methods
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Is this legal?char c = 70000;
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No, out of range, less than 65536, to make legal use cast char c = (char) 70000
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class Honda extends Car { implement methods here }Which is the parent abstract class?
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Car
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• 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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Hello
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Is this legal?final stricttfp class
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Yes because strictfp applies to classes or methods
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What does this printi.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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frogCount = 2!
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• When an array of primitives is instantiated, all elements get their default valuesT or F
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T
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Instance of using const, for a constant which key word do we use?a.staticb.finalc.private
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b.final
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a double is a 64 bit flopating pointis it signed or unsigned?
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SIGNED
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For instance variables, what is illegal? (4)
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abstract, syyncrhoized, strictfp, natvie
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//Local objects and arraysDate d ;if (d == null){System.out.println(“date is null”);}Why will this crash?
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//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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public abstract class A{ abstract void foo();}class B extends A{void foo(int I){ //will this line compile?}}
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won’t compile this is overloaded!
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Is this legal?char c = -29
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No , possible of loss of precision, need a cast, char is unsigned.
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scores = new int[3] {4,7,2} //legal?
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scores = new int[3] {4,7,2} //legal? NO – do not put size.
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An array has a ____ relationship. class Car{}, class Honda extends Car{}i.e. Car [ ] my Cars = { new Honda() };a. IS-Ab. HAS-A
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IS-A
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• If no arguments are passed to main, the length of the main String array parameter will be ____
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zero
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When an array of objects is instantiated, objects within the array are instantiated automatically.T or f?
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F
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A char is a unicode char.. how many bits.8,16,32,64?
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16 bit unsigned.
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Is this legal?int[5] scores;
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No, never legal to include the size of array in declaration
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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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yes because its in the same package
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Is this legal?final abstract class
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NO, a class can never be FINAL AND ABSTRACT. contradiction abstract(has to be extended), final can’t
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Both short and byte are SIGNED integers.How many bit does a bye have?
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8
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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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NO
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Abstract Methods: declared but not implemented, required to be ________a. extendedb. declared
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extended
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Why is this illegal?int x = 1; if (x) { }
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Because x is not "true" or "false"
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Abstract class MKUST BE1. Instantiated2. Extended (sublcasses)3. BOTH
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2. Absturact classes can ONLY be extended NEVER instantiated
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Is this legal?
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No because arrays must always be given a size at the time they are constructed.
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Both short and byte are SIGNED integers.How many bit does a short have?
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16
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a long is a _____ bit ______ integer
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64 signed
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Is this legal abstract strictfp class Blah?
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Yes because strictfp applies to classes or methods.
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This deinfes what kind of character?char c = ‘\”’; 1. double quote2. single quote
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1. double quote
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• 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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False
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an int is a a 32 bit SIGNED or UNSIGNED ?
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SIGNED
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Why is this illegal ?public int break(int b) { }public int switch(int b) {}
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break and switch are reserved key words
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• int[ ] [ ] books new int [3] [];• int [ ] numbers = new int[6];• int aNumber = 7;• books[0] = numbers //
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Compile? Yes, numbers is an int array.
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public/private/default/protected synchronized method ?legal?
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YES
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From broadest to the narrowest which is the correct order?double float, long, int, byte, shortdouble, float, int, long, byte,shortdouble, long, flat, short, int , bytedouble, float, long,int, short, byte
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double, float, long,int, short, byte
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public final class ? Is this legal?
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Yes because of inheritance
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Strictfp => used for both Classes and what kind of methods:
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non-abstract methods
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Legal?int [] scores;scores = new int[] {4,7,2};
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YES/used for just in time array
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Why is this illegal ?public int break(int b) { }public int switch(int b) {}
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break and switch are reserved key words
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How do you intilize array of dotsin one line as a list.
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int[] dots = {3,6,x,8};
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Will this compile?abstract class Car{ private double price; public abstract void goFast();}
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YES
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strictfp can modify which of the followingclassmethodvariable
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class AND method ONLY
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Is this legal?char b = 982;
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Yes because its an int literal
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synchronized final class?compiles?
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NO because synchronized only applies to methods
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Which keyword is not implmeneted in java because its harmful?a. abstractb. gotoc. transient
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b. goto
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