Source File - Arithmetic Operator Substitution
Nov 6, 2014
My goals:
1) Have some source file be read in
2) Specify what arithmetic operators to swap (+, -, /, *)
2) If an arithmetic operator is read (like a + sign etc) then we swap it with its opposite (- for example)
3) Once the swap is complete, the rest of the file stays the same even if more operators are in the file...it is then output to a file (I am going with 1mutation.java)
4) This is where it gets tricky....it then picks up where it left off to finish reading the + operators (or whatever was specified) and repeats steps 2-3 (but the operator that is already swapped gets left as it was / skipped) and the output is saved as 2mutation.java.
The most I have been able to manage is having it changed 1 operator or all of them at once. I deleted a lot of my work to start fresh / master one operator for the time being. Here is what I have:
import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
public class OperatorSub {
[Code] ....
This is the data file I am using. (see attached) The file should be .java or .cpp but I stuck with .txt for now. How to tackle this? Am I on the right track?
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Jul 29, 2014
I am trying to encrypt a string using substitution cipher, the program doesnt show any errors but the output is not what is expected. On encryption it shows random characters whereas i want it to be encrypted by another letter. This is what I have done:
/* Encryption using substitution */
import java.io.*;
public class SSExp1 {
public static void main(String args[]) {
char[] ip= new char[20];
char[] op= new char[20];
char key = '3';
String b;
[Code] .....
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// create output directory if it doesn't exist
if(!dir.exists()) dir.mkdirs();
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[Code] ....
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public static void copyFile(File source, File destination) {
BufferedReader br;
try {
FileWriter fw = new FileWriter(destination.getAbsoluteFile());
PrintWriter bw = new PrintWriter(fw);
br = new BufferedReader(new FileReader(source));
String line = new String();
[Code] ....
As shown in the source.txt file, there are 4 lines in the file but when the execution gets to while ((line = br.readLine()) != null) , it executes to false.. Why this is so?
below is the source.txt file
12 is a number
Green is bad
5 is not so cool
you are right
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@echo off
echo Compiling %1 with JNA and JFreeChart...
javac -Xlint:deprecation -cp "C:jna-master*;C:jfreechart-1.0.19libjfreechart-1.0.19.jar;C:jfreechart-1.0.19libjcommon-1.0.23.jar;."%*
The file to compile is in C:MindWaveTestsReadMindWave.java
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Jun 8, 2014
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For example:
Enter your source code:
D:Data StructsProjectssrcHelloWorld (I didn't put .java on purpose)
Exception in thread "main" java.io.FileNotFoundException: D:Data StructsProjectsAssignment 3srcHelloWorld (The system cannot find the path specified)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(Unknown Source)
at java.io.FileInputStream.<init>(Unknown Source)
at java.io.FileReader.<init>(Unknown Source)
at HomeworkDriverFour.main(HomeworkDriverFour.java:14)
//Can I get rid of the exception above and replace it with "File not found!"
Enter your source code:This is what I have so far:
import java.io.*;
import java.util.*;
public class HomeworkDriverFour {
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
[code]...
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Jan 22, 2015
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class Movie
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String title;
String genre;
int rating;
void playit()
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System.out.println("playing the movie");
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}
public class MovieTestDrive
[code]....
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Mar 30, 2014
To be specific, how can I use enumeration of one source-code file in another.
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Oct 9, 2014
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Does the statement above mean the following should compile fine ?
public class Animal{
public class Animal{ }
}
The author gives an example saying that if you have a class Multiple.java and in that class, you have:
public class Multiple{}, then it should compile.
But this does not compile. I tried it.
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Nov 3, 2014
I am having hard time to grasp the concept of java as i am beginner. according to different sources found in internet, only one class is written in one source file. and all those class can be accessed through the main class.
my question is
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2.can we create more than 1 class in same source file?is there special way to do it? i do get error always when i try to do so
3.can multiple classes contain main method? or should there be only single class containing it?
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Jan 25, 2014
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My code is currently (in a try/catch)
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Feb 10, 2015
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// code goes here...
}
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And the Something.java is inside the following structure...
A.jar
com/
mycompanyA/
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Another.class
B.jar
com/
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neededImage.gif
bin-folder/
org/
apache/
Something.java
To compile this code(Something.java) from command line I want to use the following command,
javac org/apache/Something.class
And for the compilation to be successful, I'll have to be just above bin-folder because...
- > Only then my default class path will be (.) and java would automatically include A.jar and B.jar(the other way is to add the jar files using -cp argument, which I want to avoid in this scenario)
- > And for the import org.mycompanyX to work I'll have to be in the (.) directory.
Are my assumptions correct about how java find jar contents imported in a source file?
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Oct 20, 2014
I have a question about the following snippet concerning the steps the javac compiler follows to compile a program:
[...]at first, searching a class within a package is discussed if the latter doesn't contain a full package name[...]
It is a compile-time error if more than one class is found. (Classes must be unique, so the order of the import statements doesn't matter.)
The compiler goes one step further. It looks at the source files to see if the source is newer than the class file. If so, the source file is recompiled automatically. Recall that you can import only public classes from other packages. A source file can only contain one public class, and the names of the file and the public class must match. Therefore, the compiler can easily locate source files for public classes.
However, you can import nonpublic classes from the current package. These classes may be defined in source files with different names. If you import a class from the current package, the compiler searches all source files of the current package to see which one defines the class. I don't quite understand the red fragment. I wondered if the word "import" nonpublic classes from the current package weren't a synonym for the word "use", since why would we want to import a class from the same package when compiler searches the current package automatically anyway?
However I wanted to test nonpublic classes that are contained in source file which name doesn't match the class name:
NonpublicClass.java:
Java Code:
package com.work.company;
class NonpublicClass
{
public void description() {
System.out.println("Working!");
}
} mh_sh_highlight_all('java');
[Code] ....
Everything's fine when the source file names are the same as above. However, when I change NonpublicClass.java to a different name, there's an error "cannot find symbol" in:
Java Code: NonpublicClass v = new NonpublicClass(); mh_sh_highlight_all('java');
I noticed that the class file for NonpublicClass isn't even generated so that's probably the cause. If I change to the directory of the package the NonpublicClass is contained in and compile it directly, i.e. issue for example:
Java Code: javac NonpublicClass_different_name.java mh_sh_highlight_all('java');
Then a proper class file is generated with the class name, that is NonpublicClass.class, and afterwards I can compile the main program in Start.java.
So the question is what am I missing regarding the cited quote that reads:
If you import a class from the current package, the compiler searches all source files of the current package to see which one defines the class.
? Because adding such an import to CompanyClass.java:
import com.work.company.NonpublicClass;
didn't work either...
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Feb 3, 2014
Why is this not valid in java:
Both uses public with the same class/interface name.
Test.java:
public class Test implements Test{
/// Some codes
}
public interface Test {
///Some methods
}
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Oct 31, 2014
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import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.JPasswordField;
[code]....
Eclipse error message:
Exception in thread "main" java.lang.NullPointerException
at javax.swing.ImageIcon.<init>(ImageIcon.java:205)
at GUI.<init>(GUI.java:26)
at Apples.main(Apples.java:7)
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Aug 6, 2014
How do i go about developing a simple arithmetic tester program which can be used to support young children improve their arithmetic skill. The program should accepts string data for the player's name and the number of questions they want to try, which will be entered by the user. The program should take in the following inputs from the user:
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The number of sums that the user wants to attempt. This number must be a whole number, and be between 2 and 50 inclusive.
The program must check that the values entered fall within the valid ranges. The program must also check that no empty strings are entered for names.
Once the player has entered their name and the number of questions they want to attempt, the game begins. The program must generate sums for the player.
The program should generate one question at a time and display the question for the user. The questions must involve two numbers and be either a multiplication, division, subtraction, or addition. For example, the following are all valid questions:
3 * 4 = ?
8 / 2 = ?
7 + 1 = ?
9 - 8 = ?
The first number, second number, and arithmetic operator (multiply, divide, add, subtract) should all be chosen randomly, the program should Generate a new random number for each of the three parts of each sum. this requires you to choose one of the four symbols based on which random number is returned.
A few checks must be carried out before a generated question is displayed to the user. If the question is an addition question, no checks are required. If the question is a multiplication question, no checks are required. However, checks are required for subtraction and division sums.
If the question is a subtraction question, the program must check that the second number is equal to or smaller than the first number. Whilst the second number is larger than the first number, new numbers should be generated.
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Jan 8, 2014
I just cant seem to understand the order of precedence here.
class Test{
public static void main(String[] args){
int k = 1;
k += (k = 4) * (k + 2);
System.out.println( k );
}
}
From what I have read compound operators have the lowest order of precedence... But the above piece of code makes the assignment k = 1 + (k = 4) * (k + 2) before evaluating the rest of the statement first.
It then evaluates (k = 4) and proceeds with the remained of the statement 1 + 4 * (4 + 6)....
I dont understand why the first k is assigned 1 but the remaining ks 4. Should they not all be 1 or 4 (I would have thought 4, since += has the lost order of precedence so is evaluated last)??
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May 23, 2015
After the executing the code below:-
class Test
{
public static void main(String [] args)
{
String s = new String("new") ;
String d = new String("new") ;
System.out.println((s==d)+ " "+s.equals(d)) ;
System.out.println(s==d + " "+ s.equals(d)) ;
}
}
OUTPUT:- false true
false
Why did the output change in the second print statement?
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Nov 21, 2014
import java.util.*;
public class TestArithmetic {
public static void main(String [] args) {
Scanner console = new Scanner (System.in);
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int x1 = console.nextInt();
System.out.println("Enter Second Number");
[code]...
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1 + 2 + 3 - 4
1 + 2 + 3 * 4
1 + 2 + 3 / 4
..
1 / 2 / 3 / 4
(parenthesis can be ignored for this program)
This is what I have so far, but I don't know how to continue:
import java.util.Scanner;
public class ArithmeticComputation{
public static void main(String[] args) {
Scanner stdin = new Scanner(System.in);
int num1 = stdin.nextInt();
[Code] ....
I'm looking for a method that allows me to assign char into actual operators, so that I can loop through all the computation.
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package javalearning;
import java.util.Scanner;
public class QuadraticFormula {
public static void main(String[] args){
Scanner input = new Scanner(System.in);
System.out.print("Enter value for B: ");
double B = input.nextDouble();
System.out.print("Enter value for A: ");
double A = input.nextDouble();
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double C = input.nextDouble();
double negativeOfB = -B;
[code]....
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public void actionPerformed(ActionEvent e)
{
Object source = e.getSource() ;
int deckSiz = (int) Decks.getSelectedIndex() ;
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[code]....
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I want to catch the exception in my program is the below way:
class Temp
{
public static void main(String s[])
{
try
{
int x=10/s.length;
System.out.println(x);
[Code] ....
I am expecting my program should give output as "java.lang.ArithmeticException: / by zero" but is giving
Temp.java:11: error: ')' expected
catch (ArithmeticException e | ArrayIndexOutOfBoundsException e)
^
Temp.java:11: error: ';' expected
catch (ArithmeticException e | ArrayIndexOutOfBoundsException e)
^
Temp.java:16: error: 'catch' without 'try'
catch (Exception e)
^
Temp.java:22: error: reached end of file while parsing
}
^
4 error
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