I need to use the binary search on the sorted list, not the original list "mylist". I need to serch for a value in the sorted list. Try mixing up the numbers to really see the problem. Thanks for the reply.
Hello friends. I'm working on a program to sort a list object using toArray, Arrays.sort, and Arrays.asList. The problem asks that I then apply Collections.binarySearch directly to the list object. I know what the problem is (which I have stated through comments in my code) but I don't know how to resolve it. Here is my code :
import java.util.*;
//begin class PartC
public class PartC
{
//begin main method
public static void main(String args[])
{
//construct ArrayList object
ArrayList<Integer> mylist = new ArrayList<Integer>();
//ArrayList<Integer> newlist = new ArrayList<Integer>(mylist);
//initialize scanner
Scanner scan = new Scanner(System.in);
//ask user how long the list will be
System.out.println("Enter the number of values to be added to the list");
int nums = scan.nextInt();
//ask user to input each value separated by the enter key
System.out.println("Input the values");
//add all values to the list
for(int index = 0; index<nums; ++index)
{
int input = scan.nextInt();
mylist.add(input);
}
Object[] a = mylist.toArray();
Arrays.sort(a);
System.out.println(Arrays.asList(a));
//not working because mylist is not sorted in ascending order
//must make sorted list the parameter for the Collections.binarySearch
System.out.println(mylist);
System.out.println("Enter the value you want to search for");
int searchValue = scan.nextInt();
int where = Collections.binarySearch(mylist, searchValue);
System.out.println("The value you searched for is at index " + where);
}//terminates main method
}//terminates class PartC
I'm trying to use size() but I am getting incompatible type errors like these: G:\Java 3\vector4.java:18: incompatible types found : int required: java.lang.Character Character oper = opVect.size(); ^ G:\Java 3\vector4.java:23: incompatible types found : int required: java.lang.Character oper = opVect.size(); ^ G:\Java 3\vector4.java:33: incompatible types found : int required: java.lang.String String oper = opVect.size(); ^ Any suggestions on how to resolve this? Thanks alot for your time.
You can achieve that by using a table with three rows. Set the top and bottom rows height to 10% and make the middle row 80%. However, this doesn't use divs and it looks like you want to. Sorry if this post is totally useless to you.
The code segment I provided earlier is just to get the numbers into the list. Sorry, but I don't know that much about random numbers. Try searching on google.com.
Scanner scan = new Scanner(System.in);
System.out.println("Enter how many numbers will be added");
int nums = scan.nextInt();
System.out.println("Input the numbers");
for(int index = 0; index<nums; ++index)
{
int input = scan.nextInt();
numero.add(input);
}
That's how I add user input numbers into the list. By the way. Are you Italian?
First you can have the user input the number of values to input into the data structure(arrays are a good choice). Then use a for loop to ask the user to put in each value.
What line(s) of my program make the compiler think that I'm trying to access the 43rd element? Also, I want to remove the last element of the vector to simulate a pop for stacks. How can I accomplish that? Thanks for the reply.
Hello, I'm facing another problem with vectors, this time with the problem of converting infix to postfix. The compile process completes, but I recieve an error after I enter the infix expression. Here is the exact error I recieve:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 43 >= 2 at java.util.Vector.removeElementAt(Vector.java:511) at vector4.InToPost(vector4.java:22) at vector4.main(vector4.java:79)
Process completed.
I don't really know what is wrong with my code and why I am recieving the error. Here is my code:
import java.util.*;
public class vector4
{
public static String InToPost(String infixString)
{
//operator vector initialized
Vector<Character> opVect = new Vector<Character>();
//postfixString initialized as empty
String postfixString = "";
//scan infix strring and take appropriate action
for(int index = 0; index<infixString.length(); ++index)
{
char chValue = infixString.charAt(index);
if(chValue == '(')
opVect.add('(');
else if(chValue == ')')
{
Character oper = opVect.lastElement();
while(!(oper.equals('(')) && !(opVect.isEmpty()))
{
postfixString += oper.charValue();
opVect.removeElementAt(opVect.lastElement());
oper = opVect.lastElement();
}//end while loop
opVect.removeElementAt(opVect.lastElement());
}//end else if
else if(chValue == '+' || chValue == '-')
{
if(opVect.isEmpty()) //operatorStack is empty
opVect.add(chValue);
else //current operatorStack is not empty
{
Character oper = opVect.lastElement();
while(!(opVect.isEmpty() || oper.equals(new Character('(')) || oper.equals(new Character(')'))))
{
opVect.removeElementAt(opVect.lastElement());
postfixString += oper.charValue();
}//ends while loop
opVect.add(chValue);
}//end else
}//end else if
else if(chValue == '*' || chValue == '/')
{
if(opVect.isEmpty())
opVect.add(chValue);
else
{
Character oper = opVect.lastElement();
while(!oper.equals(new Character('+')) && !oper.equals(new Character('-')) && !opVect.isEmpty())
{
opVect.removeElementAt(opVect.lastElement());
postfixString += oper.charValue();
}//end while loop
opVect.add(chValue);
}//end else
}//end else if
else
postfixString += chValue;
}//end for …
Wow! I turns out he was right! I had a Vector.class file in the same directory. Deleting that solved the problem. Thanks again to both of you for the help.
Hello, I'm trying to write a program that evaluates a postfix expression using the vector class. I have done this successfully using stacks but I am experiencing trouble with vectors. Here is the error message I am recieving:
I:\vector.java:26: type Vector does not take parameters public static int evalPostfix(String str, Vector<Object> opndVect) ^ I:\vector.java:79: type Vector does not take parameters Vector<Object> myvect = new Vector<Object>(); ^ I:\vector.java:79: type Vector does not take parameters Vector<Object> myvect = new Vector<Object>(); ^ 3 errors
Process completed.
Here is my code:
import java.util.*;
public class vector
{
public static int convert(char chValue)
{
switch(chValue)
{
case '0': return 0;
case '1': return 1;
case '2': return 2;
case '3': return 3;
case '4': return 4;
case '5': return 5;
case '6': return 6;
case '7': return 7;
case '8': return 8;
case '9': return 9;
default:
{
System.out.println("Error in evaluation");
return -1;
}//terminates default
}//terminates switch
}//terminates text of convert method
//begin coding for evalPostfix method
public static int evalPostfix(String str, Vector<Object> opndVect)
{
for(int index=0; index<str.length(); ++index)
{
//if current char is an integer
char chValue=str.charAt(index);
if('0'<=chValue && chValue<='9')
//add the converted integer digit to the operand vector
opndVect.add(convert(chValue));
else
{
int opnd1=opndVect.get(opndVect.lastElement());
opndVect.remove(opndVect.lastElement());
int opnd2=opndVect.get(opndVect.lastElement());
opndVect.remove(opndVect.lastElement());
switch(chValue)
{
case '+':
{
int value=opnd1+opnd2;
opndVect.add(value);
break;
}//end case +
case '*':
{
int value=opnd1*opnd2;
opndVect.add(value);
break;
}//end case *
case '-':
{
int value=opnd1-opnd2;
opndVect.add(value);
break;
}//end case - …
I was able to compile and run the code successfully by separating all the files and creating an additional driver class. Thanks again for all the help.
I tried without the asterisks but recieved the same error message which reads: F:\Java\GeometricObject.java:7: package Triangle.java does not exist import Triangle.java.*; ^ F:\Java\GeometricObject.java:8: package Isosceles.java does not exist import Isosceles.java.*; ^ F:\Java\GeometricObject.java:9: package Equilateral.java does not exist import Equilateral.java.*; ^ I'm doing this in my GeometricObject file. Thanks again for all your help.
I have rewritten my program with your suggestions but I am still getting the same error message.
abstract class GeometricObject
{
//signature for perimeter method
public abstract double perimeter();
//begin class Triangle
public class Triangle extends GeometricObject
{
//explicit constructor
public Triangle(double s1, double s2, double s3)
{
this.side1=s1;
this.side2=s2;
this.side3=s3;
}//terminates constructor
//perimeter method
public double perimeter()
{
return side1+side2+side3;
}//terminates perimeter method
//local data fields
private double side1;
private double side2;
private double side3;
}//terminates text of class Triangle
//begin class Isosceles
public class Isosceles extends Triangle
{
//constructor
public Isosceles( double EQside, double otherside)
{
super(EQside, EQside, otherside);
}//terminates constructor
//local data fields
private double EQside;
private double otherside;
}//terminates class Isosceles
//begin class Equilateral
public class Equilateral extends Isosceles
{
//constructor
public Equilateral(double side)
{
super(side, side);
}//terminates constructor
//local data field
private double side;
}//terminates class Equilateral
For isosceles I used three parameters in the constructor call to match the Triangle constructor. For equilateral I used two parameters in the constructor call to match the isosceles constructor. I thought this was the right way to do it but I am obviously wrong. Thanks again for any help.
Oh, right. So all of the constructor calls need to have the same number of parameters, but the parameters in the constructor definitions don't need to be the same in number, right? Thanks for your help, jasimp.
Hello. I'm working on a class hierarchy that starts with an abstract class called GeometricObject. I want to use this class to create classes of different types of triangles. I want to these classes to inherit the perimeter method from the Triangle class. Here's what I have so far.
abstract class GeometricObject
{
//signature for perimeter method
public abstract double perimeter();
public class Triangle extends GeometricObject
{
//explicit constructor
public Triangle(double s1, double s2, double s3)
{
this.side1=s1;
this.side2=s2;
this.side3=s3;
}//terminates constructor
//perimeter method
public double perimeter()
{
return side1+side2+side3;
}//terminates perimeter method
//local data fields
private double side1;
private double side2;
private double side3;
}//terminates text of class Triangle
public class Isosceles extends Triangle
{
//constructor
public Isosceles( double EQside, double otherside)
{
super(EQside, otherside);
}//terminates constructor
//local data fields
private double EQside;
private double otherside;
}//terminates class Isosceles
public class Equilateral extends Isosceles
{
//contructor
public Equilateral(double side)
{
super(side);
}//terminates constructor
//local data fields
private double side;
}//terminates class Equilateral
}//terminates class GeometricObject
I'm recieving the following error message:
F:\Java\GeometricObject.java:35: cannot reference this before supertype constructor has been called
super(EQside, otherside);
^
F:\Java\GeometricObject.java:46: cannot reference this before supertype constructor has been called
super(side);
^
There is obviously something wrong with the 2 lines starting with super, but I have not been able to figure it out. Thanks to everyone in advance for any help.
Off the top of my head, I'm pretty sure you must use: <select> <option> whatever you want in drop down menu</option> repeat this for as many items you want in the drop down menu. Be sure to enclose all of these items in option tags. Also make sure to close your select tag. Hope this examples helps.
Sorry, I didn't mean that I would just give them the program. I was just saying that I have it correctly completed if anyone needs help. I respect the forum rules and would never go against the policy. I know that it is important for fellow viewers to solve their own problems by themselves with just a liitle help from the community. Sorry once again for the implications of my previous post.
If anyone needs help with this particular problem (converting infix to postfix and evaluating), send me a message. I have a working version of the program and I'd be glad to help.
I don't watch anime, but anime video games are awesome. I love Tales of Symphonia, Tales of the Abyss, Tales of Vesperia, the Star Ocean series, and the Final Fantasy Series. Any one agree?
Hey, I always listen to the Bronx Underground band If But When (my brother is the bass player). They have a really unique pop-rock sound. Check out their debut EP on iTunes and check out the newly redesigned myspace page at www.myspace.com/ifbutwhen. By the way, sorry for the advertisement, but they really are awesome.
Thanks for backing me up, verruckt24. It is good to see that not everyone in this forum is so cynical and suspicious. I made some ajustments to my program and got it to work. Thanks for your help.
u need to implement the stack then do precedence with switch cases ill give more info once i get home, but at least show some code that you wrote not the code from your resource material form CD
I implemented the stack interface and the class containing all of the methods(pop, push, etc.) and I'm pretty sure there are no errors there. I wrote this code myself, I didn't copy it from a CD or website. Also, I know for a fact that converting from infix to postfix can be done without using a switch statement. Thanks for the reply though.
Hello. I'm trying to write a program that will convert a user input infix expression into its postfix form. My current code is allowing the user to input a string, but it does nothing with the string. I'm fairly new to JAVA, thus I think I'm making a simple mistake in the main method. I'm using a generic class for a stacks implemented using arrays to store any data type. Thanks in advance for any help.
import java.io.*;
import java.util.*;
//begin coding for the stack interface
interface Stack<E>
{
public boolean isEmpty();//tests is current stack is empty. Returns true if so, and false if not.
public E top() throws StackException;//retrieves value at the top of the stack. Stack cannot be empty.
public void push(E value) throws StackException;//pushes a value on the top of the stack.
public void pop() throws StackException;//removes a value from the top of the stack. Stack cannot be empty.
}//terminates coding of Stack interface
//begin coding for the objArrayStack class
class objArrayStack<E> implements Stack<E>
{
//constructor
public objArrayStack()
{
topValue=-1;
}//terminates constructor
public void push(E value)throws StackException
{
if(topValue<ArraySize-1)//currrent stack is not full
{
++topValue;
Info[topValue]=value;
}//terminates if
else //current stack is full
throw new StackException("Error: Overflow");
}//terminates push method
public void pop() throws StackException
{
if(!isEmpty())//current stack is not empty
--topValue;
else //stack is empty
throw new StackException("Error: Underflow");
}//terminates pop method
public boolean isEmpty()
{
return topValue==-1;
}//terminates isEmpty method
public E top() throws StackException
{
if(!isEmpty())//stack is not empty
return (E)Info[topValue];
else //stack …
