Category Archives: Computer Science

How to Access 1 digit at at time of an int in Java

How to access each digit in an int in Java

 

Array Fun 3 [Resizing] Version 2

Version 1

ArrayFun3 - Please call your class that , exactly. Yes, you will lose a point for not following this simple specification.

  • use meaningful variable names
  • use  camelCase for variable and method names
  • use  i  as the variable name for for-i loops . Remember – programming is generally done in teams so your code should be  as expressive as possible. Use conventions to convey meaning, not cause confusion.
  • do not use i as the variable name in for-each  loops. Again, this would be misleading and imply you’re using a different type of loop.
  • do not import any external libraries . All solutions can be done by making use of variables and arrays and some basic math ; nothing more is needed.

 

int[]  removeZeroes(int [] nums)

Description: This method returns a version of nums  in which all occurrences of 0 , zero, are  removed

Method Call return value/output
noZeroes(  { 3 , 4, 0, 1} ) { 3, 4, 1}
noZeroes(  { 0, 5 , 0, 0, 9, 0, 1 , 11} ) { 5,9,1,11}

String[]  removeNulls(String[] strs)

Description: This method returns a version of  strsin which all null values are removed. Note: removeNullsv2

 

int[] digitsToArray(int n)

@precondition n > 9

Description: This method takes each digit in the integer n  and stores it in an array in reverse order, as shown below. First, make sure you understand the code here. , which btw, testers had to figure out , on the fly, in a previous AP A test.

digitstoarray

int[] removeLeadingZeroes(int[] nums)

@precondition nums.length >=2 

Description: This method returns an array in which all elements that meet the 2 criteria below are removed.

  • the element has a value of 0, zero
  • the element’s index is less than the index of the first element whose value is not zero.

 

remove_leading_zeros

 int[]  doubleUp( int  [] nums, int val)

@precondition nums.length >=2 

Description: This method returns a version of nums –with all occurrences of val   duplicated.

Method Call return value/output
doubleUp(  { 3 , 4, 0, 1}  , 4  ) { 3, 4 , 4, 0, 1}
doubleUp(  { 1, 3 , 1, 5 , 3, 3} ,  3 )    {1 , 3, 3  , 1, 5 , 3, 3, 3, 3 }

 

 

 

Similar problems on codingbat

Pre4

Unit 2 Extra Credit

In addition to the required Unit 2 Creative Task, if you want some extra credit, you can do the following assignment:

Research how groups work in CMU ( see the docs)

Write a program that

  • includes two functions
  • minimum of 5 objects
  • A group comprised of at least 3 objects
  • One of the functions must change the properties of all things in the group.

You can write this in one of empty creative a tasks.

CMU Unit 2, creative task – mousepress mousedown

For this creative task,

This is a 10 Point assignment:

To get 9 points:

  • minimum of 2 shapes
  • minimum of 2 functions
    • 1 must be a mouse function (mousePress, mouseMove, mouseRelease)
    • the other function can be any function at all
    • one of the functions must change a property (fill, width etc) of the shape

To get the 10th point,

Research how groups work in CMU ( see the docs),

  • Use a  group comprised of at least 3 objects
  • 1of the functions must change the properties of all things in the group.

Bs4 template

Copy and Paste the HTML file below into its own file

Updated Version:

 

 

Version 1:

 

SUPA – Web 2022-23

Quarter 4 project

 

Prior iterations : https://mrmonline.org/supa-2020/ , https://mrmonline.org/web-design-programming-18-19/

 

Templates

Bootstrap

Vim 

SeatingChart Java OOP Project – 2D Arrays

Let’s write a program for something like PowerSchool that helps organize a seating chart for students.  There is a tester file at the page’s bottom.

First class : Student  , from https://mrmonline.org/student-class/

Class SeatingChart

This class mainly manages a 2-d  array of student objects. Note: an empty seat in the chart will be designated by a null value.

Constructor(s)

  • public SeatingChart(int per, String teacher, String _rosterName) Initializes parameters to respective arguments and creates a 2-d array  of null objects with default dimensions DEFAULT_ROWS , DEFAULT_COLS
  • public SeatingChart(int per, String teacher, String _rosterName, Student[][] table)

Methods:

public String getTeacherName() // returns teacherName

public String getRosterrName() // returns  rosterName

public int getPeriod()  // returns period

public int countEmptySeats() ; //returns the number of empty seats. As noted earlier, an empty seat is represented by a null value in the 2-d array of student s

Student[][] getStudentChart()  @returns chart

public int[] indexOf(Student stu);  returns a 2 element array representing the row and column position of stu in chart ; [-1 , -1] should be returned if stu is not in chart

public boolean setSeat(int row, int col, Student stu) -  places Student Stu  at that row and column .  This can only be done if there is no student in that location. If a student already inhabits that row and column then the method should return false and not make any changes to chart .

public void swap(Student s1, Student s2) // this swaps the locations of s1 and s2

public Student getStudent(int row, int col) returns the student at the given row and col ; or null if the seat is empty

public void removeStudentAt(int row, int col)   sets value of object at  row  and  col  to  null 

public boolean equals(SeatingChart other) // returns true if all aspects of  other are equivalent to self.

public void colMajorForm() . This prints out the student chart in column major form.   Examine the diagram below showing an example seating chart on the left and the printed output on the right.seating chart col major

public String toString(); //follow the conventions we have been using. When you print out the chart , let’s show "E!" t o indicate an empty seat; for seats with students, just display their name.SeatingChart to string v2

public Student oldest() // returns the student object with the greatest age

Extra credit

public void randomize() // this randomizes the chart. Please be prepared to meet with me to discuss your code. (You cannot use a library to do all the work, if such a library even exists)

 

SeatingChartTesterv2.java :

import java.util.Arrays;

public class SeatingChartTesterv4
{
    public SeatingChartTesterv4()
    {
    p("v4, null constructor checks");
    Student amelia = new Student("Amelia", 17);
    Student antonioooo = new Student("antonioooo", 14);

    SeatingChart period3 = new SeatingChart(3, "Mr. M", "A Days");

    
    int correct = 0;
    int wrong  = 0;

    boolean didNotInit = false;
    
    
    if(period3.getTeacherName() == null)
     {
        p("*non* default constructordid not initialize teacherName");
        wrong++;
        didNotInit = true;
        }
    else
     correct++;
        
    if(period3.getRosterrName() == null)
     {
        p("*non* default constructor did not initialize rosterName");
        wrong++;
                didNotInit = true;
        }
    else
     correct++;
       if(period3.getStudentChart() == null)
     {
        p("*non* default constructor did not initialize chart");
        wrong++;
                didNotInit = true;
        }
    else
     correct++;
     
     if ( didNotInit == true)
     {
        throw new Error("You must fix your constructor (non default) before doin anything else \n\t exiting tester");
         
         
     }
     // now let's do the same for default  constructor
                     //SeatingChart(int per, String teacher, String _rosterName
     SeatingChart dfault = new SeatingChart( 2, "Mr. Lorensax", "periods 2 ");
     
     if(dfault.getRosterrName() == null)
     {
        p(" default constructor did not initialize rosterName");
        wrong++;
                didNotInit = true;
        }
    else
     correct++;
       if(dfault.getStudentChart() == null)
     {
        p(" default constructor did not initialize chart");
        wrong++;
                didNotInit = true;
        }
    else
     correct++;
     
     if ( didNotInit == true)
     {
        throw new Error("You must fix your constructor (  default) before doin anything else \n\t exiting tester");
         
         
     }
     //end  non default constct test
     
     
    Student[][] currentChart = dfault.getStudentChart();
    if(currentChart[0].length == SeatingChart.DEFAULT_COLS && currentChart.length == SeatingChart.DEFAULT_ROWS)
        correct++;
    else
        {
        p("*default constructor's 2-d Array incorrect dimensions");
        wrong++;
        }

    boolean result = period3.setSeat(5,6, amelia );

    if(result)
        correct++;
    else
        {
        p("setSeat() return value error");
        }

    Student[][] chartNow = period3.getStudentChart();
    if(chartNow[5][6] == amelia)
    {
        correct++;

        if( period3.getStudent(5,6) == amelia)
            correct++;
        else
            {
            p("Error, looks like getStudent() ");
            }

    }    
    else
        {
        p("A) erorr, probably from setSeat() or getStudentChart() ");
        wrong++;
        }



    int[] locaxn = period3.indexOf(amelia);
    if(locaxn[0]==5 && locaxn[1] == 6)
        correct++;
    else
        {
        p("B) setSeat() or indexOf() error");
        wrong++;
        }
    result =period3.setSeat(5,6, antonioooo );

    if(result== false)
        correct++;
    else
        {
        p("C) setSeat() return value error");
        wrong++;
        }

    String st = period3.toString();
    
   // System.out.println(st) ;

    if(st.indexOf("SeatingChart") == 0)
        correct++;
    else{
        p("toString() error. ClassName should be first characters");
        wrong++;
    }

    if(st.contains("Mr. M"))
        correct++;
    else{
        p("toString() error. ");
        wrong++;
    }
   
    if(st.contains("A Days"))
        correct++;
    else{
        p("toString() error. ");
        wrong++;
    }
//new seating chart
Student tim = new Student("tim");
Student[][]  someKids= {
                    { new Student("giorgio"),null,  tim , },
                    { new Student("michael"), new Student("joe", 12) , null },
                    { null, new Student("Alex"), new Student("Eliam", 999), null},
                    { new Student("Jen"),null,  new Student("antonio", 5),  },
                        };

    SeatingChart period4 = new  SeatingChart(4, "MR M", "p4", someKids);
//System.out.println( period4 );
//make sure that someKids was actually set to the chart
 if(period4.getStudentChart() == null)
        {
        wrong++;
        p("Non default constructor's chart not initialized");
        }
    else
    correct++;
    
    
Student[][] p4Chart = period4.getStudentChart();
if( Arrays.equals(p4Chart , someKids))
    correct++;
else
    {
    wrong++;
    p("Error . Looks like you did not correctly instantiate 2-d array in constructor ");
    }




    boolean isCorrect = true;
Student oldest  = null ;
    try{
    oldest = period4.oldest();
    }
    catch(NullPointerException e){
        isCorrect = false;    
            p("Error @ oldest(), you cannot call .getAge() on a null object");
        }
   
if(isCorrect && oldest != null && oldest.getAge() ==999)
correct++;
else
    {
    wrong++;
    p("Error @ oldest()");
    }
    locaxn = period4.indexOf(tim);
    



    if(locaxn[0]==0 && locaxn[1] == 2)
        correct++;
    else
        {
        p("A incorrect student. Could be constructor");
        wrong++;
        }
       
if ( period4.getStudent(0,2) == tim )
        correct++;
    else
        {
        p("B incorrect student. Could be constructor, getStudent()");
        wrong++;
        }
    ///


int emptySeats = period4.countEmptySeats();



if(emptySeats == 5)
        correct++;
    else
        {
        p("countEmptySeats() error");
        wrong++;
        }


Student vinnie = new Student("Vinnie", 16);
Student yuya = new Student("Yuya", 18);
Student[][]  p5Kids = {
                        { yuya, vinnie}
                        };

SeatingChart period5 = new  SeatingChart(4, "MR M", "p4", p5Kids);

int[]  yuyaLocation_befo = period5.indexOf(yuya);
int[]  vinniaLocation_befor = period5.indexOf(vinnie);



period5.swap(vinnie,yuya) ;
int[]  yuyaLocation_now = period5.indexOf(yuya);
int[]  vinniaLocation_now = period5.indexOf(vinnie);

if( yuyaLocation_now[0] == vinniaLocation_befor[0] &&  yuyaLocation_now[1] == vinniaLocation_befor[1]  )
        correct++;
    else
        {
        p("Error Swap");
        wrong++;
        }
if( vinniaLocation_now[0] == yuyaLocation_befo[0] &&  vinniaLocation_now[1] == yuyaLocation_befo[1]  )
        correct++;
    else
        {
        p("Error Swap");
        wrong++;
        }
////
//


Student rany = new Student("rany", 16);
Student[][]  p6Kids = {
                        { rany, null,null,null},
                        { null, null,null,null}
                        };

SeatingChart period6 = new  SeatingChart(4, "MR M", "p4", p6Kids );
period6.removeStudentAt(0,0);
if( period6.getStudent(0,0) == null )
        correct++;
    else
        {
        p("Error @ removeStudentAt() ");
        wrong++;
        }

if( period5.equals(period6) == false)
        correct++;
    else
        {
        p("A Error @ equals() ");
        wrong++;
        }
if( period5.equals(period5) )
        correct++;
    else
        {
        p("B Error @ equals() ");
        wrong++;
        }

SeatingChart period6Clone = new  SeatingChart(4, "MR M", "p4", p6Kids );

if( period6.equals(period6Clone) )
        correct++;
    else
        {
        p("C Error @ equals() ");
        wrong++;
        }




p("----------------------------------");
p("Correct : " + correct);
p("Wrong : " + wrong);


    }//end of constructor

void p(String x) { System.out.println(x); }
void p(int x) { System.out.println(x); }
void p(boolean x) { System.out.println(x); }
void p(double x) { System.out.println(x); }
void p2d(int[] x) { System.out.println(x[0] + ",  " + x[1]); }

}
SeatingChartTester