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Details Title: Java Basic Questions CH1-4 Description: Java Basic Questions CH1-4 Total Flash Cards: 80 Created: 11/02/2005 16:02:08	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term Which keyword is not implmeneted in java because its harmful? a. abstract b. goto c. transient Definition b. goto Term Instance of using const, for a constant which key word do we use? a.static b.final c.private Definition b.final Term Why is this illegal ? public int break(int b) { } public int switch(int b) {} Definition break and switch are reserved key words Term Why is this illegal ? public int break(int b) { } public int switch(int b) {} Definition break and switch are reserved key words Term A char is a unicode char.. how many bits. 8,16,32,64? Definition 16 bit unsigned. Term a double is a 64 bit flopating point is it signed or unsigned? Definition SIGNED Term A flat is a ___ bit floating point number Definition 32 Term a long is a _____ bit ______ integer Definition 64 signed Term an int is a a 32 bit SIGNED or UNSIGNED ? Definition SIGNED Term Both short and byte are SIGNED integers. How many bit does a short have? Definition 16 Term Both short and byte are SIGNED integers. How many bit does a bye have? Definition 8 Term 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 Definition double, float, long,int, short, byte Term Float f = 23.23568 fails, why? 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 Term Why is this illegal? int x = 1; if (x) { } Definition Because x is not "true" or "false" Term Char literals can also be represented as an integer, as long as it’s less than 1. 65536 2. 65537 3. 65538 Definition 1. 65536 Term This deinfes what kind of character? char c = ‘\”’; 1. double quote 2. single quote Definition 1. double quote Term Is this legal? char b = 982; Definition Yes because its an int literal Term Is this legal? char c = 70000; Definition No, out of range, less than 65536, to make legal use cast char c = (char) 70000 Term Is this legal? char c = -29 Definition No , possible of loss of precision, need a cast, char is unsigned. Term Delcare an array Two ways: before or after name a) int [ ] key; b) int key [ ] ; which is recommended (a) or (b)? Definition a Term Is this legal? int[5] scores; Definition No, never legal to include the size of array in declaration Term Declare, construct, and assign this in one line. TEST SCORES array of ints size of 4. Definition int [] testScores = new int[4]; Term Is this legal? Definition No because arrays must always be given a size at the time they are constructed. 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]; Definition yes Term How do you intilize array of dots in one line as a list. Definition int[] dots = {3,6,x,8}; Term Is this legal? Dog puppy = new Dog(“Frodo”); Dogs[] myDogs = {puppy, new Dog (“Clover”), new Dog(“Aiko”)}; Definition Yes 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? Definition 4 [{3,4}] Term Legal? int [] scores; scores = new int[] {4,7,2}; Definition YES /used for just in time array Term scores = new int[3] {4,7,2} //legal? Definition scores = new int[3] {4,7,2} //legal? NO – do not put size. 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 Definition IS-A Term int[] splats; int [] dats = new int[4]; char[] letters = new char[5]; splats = dats; // legal? Definition Ok, dats refer to an int array Term int[] splats; int [] dats = new int[4]; char[] letters = new char[5]; splats = letters //legal? Definition NO, letters refer to a char array Term • int[ ] [ ] books new int [3] []; • int [ ] numbers = new int[6]; • int aNumber = 7; • books[0] = aNumber // Compile? Definition No , expect an int array instead of int Term • int[ ] [ ] books new int [3] []; • int [ ] numbers = new int[6]; • int aNumber = 7; • books[0] = numbers // Definition Compile? Yes, numbers is an int array. Term default value for char is a.‘\u0000’ b. 0 Definition a.‘\u0000’ Term When an array of objects is instantiated, objects within the array are instantiated automatically. T or f? Definition F Term • When an array of primitives is instantiated, all elements get their default values T or F Definition T Term • Just as with array elements, instance variables are always initialized with a default value. T or F Definition T 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 Definition False Term //Local objects and arrays Date d ; if (d == null){ System.out.println(“date is null”); } Why will this crash? Definition //Will crash because you have to explicitly set d to null. A null references Is not the same as an uninitalized reference! Term • The first command-line argument is the first element in the main String array parameter. %java TestMain Hello //First arg is ____ Definition Hello Term • If no arguments are passed to main, the length of the main String array parameter will be ____ Definition zero Term HOw many public class per source code. 1. 0 2. 1 3. 2 Definition 1 Term 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’ Definition No because thtey are both in DIFFERENT packages. We can make one of the classes public to make it compile Term strictfp can modify which of the following class method variable Definition class AND method ONLY Term Is this legal abstract strictfp class Blah? Definition Yes because strictfp applies to classes or methods. Term Is this legal? final stricttfp class Definition Yes because strictfp applies to classes or methods Term public final class ? Is this legal? Definition Yes because of inheritance Term Is this legal? final abstract class Definition NO, a class can never be FINAL AND ABSTRACT. contradiction abstract(has to be extended), final can’t Term Final class : 1.can’t be subclassed, 2.no class can extend a final class. which is true? Definition both statements are Term Abstract class MKUST BE 1. Instantiated 2. Extended (sublcasses) 3. BOTH Definition 2. Absturact classes can ONLY be extended NEVER instantiated Term Will this compile? abstract class Car{ private double price; public abstract void goFast(); } Definition YES Term class Honda extends Car { implement methods here } Which is the parent abstract class? Definition Car Term Do rules of overriding apply for private methods i.e. private void jump() public void jump() Definition No it does not Term Default Members (Package restrictions) - can be accessed only if the class accessing the member belongs to the ____ package. a. different b. SAME Definition SAME 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”. } } Definition NO Term package cert; public class Parent { int x = 9 ;//default } package cert; class Child extends Parent{ public void testIt(){ System.out.println(x); // compiles? } } Definition yes because its in the same package 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 Definition YES because of inheritance 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 Definition Compiler error, trying to access it through parent reference! Term Local variables only have___ access public int x = 7 protected int x = 7 final int x = 7 static int x = 7 Definition final int x = 7 Term Abstract Methods: declared but not implemented, required to be ________ a. extended b. declared Definition extended Term public abstract class A{ abstract void foo(); } class B extends A{ void foo(int I){ //will this line compile? } } Definition won’t compile this is overloaded! Term abstract final Method? legal? Definition No, contradicts Term abstract synchronized, strictfp, native void thisMethod(); ? lega? Definition NO explains implemenation detils... Term abstract static doStuff(); Is this legal? Definition NO Term Synchronized – only applies to ______, can be accessed only one thread at a time. classses methods Definition methods Term public/private/default/protected synchronized method ? legal? Definition YES Term synchronized final method? compiles Definition YES Term synchronized final class? compiles? Definition NO because synchronized only applies to methods Term Native used only for ____implemented in a platform independent way, never combined with abstract. classes or methods? Definition methods Term Strictfp => used for both Classes and what kind of methods: Definition non-abstract methods Term For instance variables what are the 3 legal types? Definition final, transietn, volatire Term For instance variables, what is illegal? (4) Definition abstract, syyncrhoized, strictfp, natvie Term final instance variables need to be intilized by the time the _______ method appears. Definition constructor Term Do local variables get default values? Definition NO 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? Definition because we’re changing the bit pattern. (ref variable) 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 Definition frogCount = 2! Term Source File Structure: package com.geeks; import java.util.* //wild card package import import com.wicketlysmart.Foo; //Explicit class import. WIll these compile Definition YES Term Why these not compile? import java.util.ArrayList.* import java.util; 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. Term static void b(); //compile? Definition illegal, defines instance methods