Stars pattern program

[colinNeedsJavaHelp]

I need the program to prompt the user to input an odd number between 3 and 79 and then the output will look like this:

for example if they input 5:
*
**
***
****
*****

or 9:
*
**
***
****
*****
******
*******
********
*********

[colinNeedsJavaHelp]

here is my first attempt:

import java.io.*;
import java.util.*;
 
publc class MagicPrinter
{
publc static void main(String[] args);
{
String inputString;
double num1;
char a = "*";
 
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.println("How many lines? ";
inputString = br.readLine();
 
do{
for(num 1 == 1;num1>3; a++){
  for(num1 ==1;num3<80;a++){
  System.out.print(a++);
 }
   }
    }
 
 
 

[abctech]

here is my first attempt:

import java.io.*;
import java.util.*;
 
publc class MagicPrinter
{
publc static void main(String[] args);
{
String inputString;
double num1;
char a = "*";
 
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.println("How many lines? ";
inputString = br.readLine();
 
do{
for(num 1 == 1;num1>3; a++){
  for(num1 ==1;num3<80;a++){
  System.out.print(a++);
 }
   }
    }
 

Hello,
First of all taking one look at your program I can say you must be getting more than a few compile time errors!

-Giving a ';' after main()? That will make it abstract and its body will be ignored.

-A character literal needs to be enclosed in single quotes(' ') not double(" ").

-The method readLine() is capable of throwing an 'IOException'.This exception is a type of 'Java Checked Exception', such type of exceptions must be handled in a try-catch block or declared to be thrown.

- for(num1 == 1) is incorrect.
'==' is for comparision and '=' is for assignment.

Structure of a 'for' loop is :
for (initialization; termination; increment) {
statement(s)
}
The first expression of the for loop is for initialization, but instead if you carry out comparision you'll definitely get an error.

-num3<80 ?
What is num3?Where is it declared?

- There is no do-loop in Java, the loops that we have are for,while,do-while.

Please compile your program and take a good look at the exceptions you are getting, try to sort them out one by one first. If you don't understand any exception post it.

As for the logic:
say there are 3 lines then -
line 1: one *
line 2: two *'s
line 3: three *'s

See the connection between the line number and the corresponding number of stars in it.
Now generalize it.

[colinNeedsJavaHelp]

Hello,
First of all taking one look at your program I can say you must be getting more than a few compile time errors!

-Giving a ';' after main()? That will make it abstract and its body will be ignored.

-A character literal needs to be enclosed in single quotes(' ') not double(" ").

-The method readLine() is capable of throwing an 'IOException'.This exception is a type of 'Java Checked Exception', such type of exceptions must be handled in a try-catch block or declared to be thrown.

- for(num1 == 1) is incorrect.
'==' is for comparision and '=' is for assignment.

Structure of a 'for' loop is :
for (initialization; termination; increment) {
statement(s)
}
The first expression of the for loop is for initialization, but instead if you carry out comparision you'll definitely get an error.

-num3<80 ?
What is num3?Where is it declared?

- There is no do-loop in Java, the loops that we have are for,while,do-while.

Please compile your program and take a good look at the exceptions you are getting, try to sort them out one by one first. If you don't understand any exception post it.

As for the logic:
say there are 3 lines then -
line 1: one *
line 2: two *'s
line 3: three *'s

See the connection between the line number and the corresponding number of stars in it.
Now generalize it.

Yeah I realized after posting I made a ton of errors. Here is what I have now

import java.io.*;
import java.util.*;
 
public class MagicPrinter
{
public static void main(String[] args)
{
String inputString;
String = num1;
char a;
a = '*';
 
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.println("How many lines? ");
num1 = br.readLine();
 
//double num1 = Double.parseDouble(in.readLine());
num1 = 0;
do{
System.out.println(a);
a++;
}while(num1<80);
}
}
 
 

[abctech]

Yeah I realized after posting I made a ton of errors. Here is what I have now

import java.io.*;
import java.util.*;
 
public class MagicPrinter
{
public static void main(String[] args)
{
String inputString;
String = num1;
char a;
a = '*';
 
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.println("How many lines? ");
num1 = br.readLine();
 
//double num1 = Double.parseDouble(in.readLine());
num1 = 0;
do{
System.out.println(a);
a++;
}while(num1<80);
}
}
 
 

Colin,
Tell me how do we declare string literals in Java? And then check if you are doing it the right way.

Your variable 'num1' is a String or an int? You want the user to input the number of lines dont you? 1,2,3 etc are numbers(integers) not strings.

You can simply say:

DataInputStream input = new DataInputStream(System.in);
 
System.out.println("How many lines you have to print?");
int num1  = Integer.parseInt(input.readLine());

I also din't quite understand the logic behing your while loop, you want to print lines uptill num1(i.e the number of lines entered by user) or uptill 80?

Here's a link to understand the various loops properly.

And here are links to some previous problems similar to yours:

http://www.thescripts.com/forum/thread598625.html
http://www.thescripts.com/forum/thread596997.html

Have a look and then try again.

[colinNeedsJavaHelp]

Colin,
Tell me how do we declare string literals in Java? And then check if you are doing it the right way.

Your variable 'num1' is a String or an int? You want the user to input the number of lines dont you? 1,2,3 etc are numbers(integers) not strings.

You can simply say:

DataInputStream input = new DataInputStream(System.in);
 
System.out.println("How many lines you have to print?");
int num1  = Integer.parseInt(input.readLine());

I also din't quite understand the logic behing your while loop, you want to print lines uptill num1(i.e the number of lines entered by user) or uptill 80?

Here's a link to understand the various loops properly.

And here are links to some previous problems similar to yours:

http://www.thescripts.com/forum/thread598625.html
http://www.thescripts.com/forum/thread596997.html

Have a look and then try again.

I want to print lines between odd numbers 3 and 79

[colinNeedsJavaHelp]

Ok so I assigned num1 to be an integer. Then I used this after the input string:

num1 = Integer.parseInt(input.readLine());

and I get this error:

MagicPrinter.java:24: cannot find symbol
symbol  : variable input
location: class MagicPrinter
num1 = Integer.parseInt(input.readLine());
                        ^
1 error
 

[abctech]

Ok so I assigned num1 to be an integer. Then I used this after the input string:

num1 = Integer.parseInt(input.readLine());

and I get this error:

MagicPrinter.java:24: cannot find symbol
symbol  : variable input
location: class MagicPrinter
num1 = Integer.parseInt(input.readLine());
                        ^
1 error
 

Have you declared and initialized variable input in your program? If you haven't how will the compiler recognize it ?!

[colinNeedsJavaHelp]

Have you declared and initialized variable input in your program? If you haven't how will the compiler recognize it ?!

I dont really know what the variable input is for.. does that look correct though?

[r035198x]

Have you declared and initialized variable input in your program? If you haven't how will the compiler recognize it ?!

Post the code that you have now that is giving this error.

[colinNeedsJavaHelp]

Ok I now get this error:

MagicPrinter.java:26: unreported exception java.io.IOException; must be caught or declared to be thrown
inputString = br.readLine();
                         ^
1 error

This is what I have for my program:

 
import java.io.*;
import java.util.*;
 
public class MagicPrinter
{
public static void main(String[] args)
{
String inputString;
String n1;
int num1;
char a;
a = '*';
 
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.println("How many lines? ");
inputString = br.readLine();
 
StringTokenizer st = new StringTokenizer(inputString);
n1 = st.nextToken();
 
num1 = Integer.parseInt(n1);
num1 = 0;
while(num1<=79) {
System.out.println(a);
a++;
}
}
}
 

[colinNeedsJavaHelp]

here is my most recent code:

import java.io.*;
import java.util.*;
 
public class MagicPrinter
{
public static void main(String[] args)
throws java.io.IOException
{
String inputString;
String n1;
int num1;
char a;
a = '*';
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.println("How many lines? ");
inputString = br.readLine();
 
StringTokenizer st = new StringTokenizer(inputString);
n1 = st.nextToken();
 
num1 = Integer.parseInt(n1);
//double num1 = Double.parseDouble(in.readLine());
num1 = 0;
while(num1<=79) {
System.out.println(a);
a++;
}
}
}
 

The program compiles and when run it asks for how many lines.

But when you enter a number the program outputs the alphabet then followed by infinite lines of ?

Anyone know why?

[r035198x]

Ok I now get this error:

MagicPrinter.java:26: unreported exception java.io.IOException; must be caught or declared to be thrown
inputString = br.readLine();
^
1 error

This is what I have for my program:

 
import java.io.*;
import java.util.*;
 
public class MagicPrinter
{
public static void main(String[] args)
{
String inputString;
String n1;
int num1;
char a;
a = '*';
 
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.println("How many lines? ");
inputString = br.readLine();
 
StringTokenizer st = new StringTokenizer(inputString);
n1 = st.nextToken();
 
num1 = Integer.parseInt(n1);
num1 = 0;
while(num1<=79) {
System.out.println(a);
a++;
}
}
}
 

You need to put a try-catch block around the code that creates the BufferedReader

BufferedReader br null;

 try { 
       br = new BufferedReader(isr);
}
catch(IOException iO) {
      iO.printStackTrace();
}
 

[r035198x]

here is my most recent code:

import java.io.*;
import java.util.*;
 
public class MagicPrinter
{
public static void main(String[] args)
throws java.io.IOException
{
String inputString;
String n1;
int num1;
char a;
a = '*';
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.println("How many lines? ");
inputString = br.readLine();
 
StringTokenizer st = new StringTokenizer(inputString);
n1 = st.nextToken();
 
num1 = Integer.parseInt(n1);
//double num1 = Double.parseDouble(in.readLine());
num1 = 0;
while(num1<=79) {
System.out.println(a);
a++;
}
}
}
 

The program compiles and when run it asks for how many lines.

But when you enter a number the program outputs the alphabet then followed by infinite lines of ?

Anyone know why?

That is what you told it to print

while(num1<=79) {
System.out.println(a);
a++;
if a is 'a', a++ makes a 'b'.

Do not use char for this. Use string or StringBuilder

if you have

String string = "*";

To add another star you simply do

 string = string + "*"; 

[colinNeedsJavaHelp]

What is the difference?

[DeMan]

not a lot.

[r035198x]

What is the difference?

char and String are different. char is a primitive type while String is class Type.
char can only hold one char value. You cannot use char to represent

****. For that you need the String type. You may want to find some time to read this one day

[DeMan]

and for the record (before everyone jumps in)....the "not a lot" was in response to a thread entitled "a" that said "what's the difference" without the preceding discussion.....
My Bad!!!!

[r035198x]

and for the record (before everyone jumps in)....the "not a lot" was in response to a thread entitled "a" that said "what's the difference" without the preceding discussion.....
My Bad!!!!

I just merged the threads.

[DeMan]

I gathered someone had.....I just didn't want to look anymore stupis than I already have ;)

[abctech]

Hi,
Couldn't resist, remembered the times when I just started with programming and would be equally confused about these * programs.

OP,
I've used Thread.sleep() so you can actually see what output you are getting due to using char a = '*' ; This method will slow your output a bit and allow you to take a good look at every line.

import java.io.*;
import java.util.*;
 
public class MagicPrinter
{
    public static void main(String[] args)throws IOException,InterruptedException
    {
        String inputString;
        String n1;
        int num1;
        char a = '*';
 
//for the input stream
        InputStreamReader isr = new InputStreamReader(System.in);
//needed to use ReadLine()
        BufferedReader br = new BufferedReader(isr);
 
        System.out.println("How many lines? ");
        inputString = br.readLine();
 
        StringTokenizer st = new StringTokenizer(inputString);
        n1 = st.nextToken();
        System.out.println("n1: " + n1);        
 
        num1 = Integer.parseInt(n1);
        System.out.println("num1: " + num1);
        num1 = 0;
        while(num1<=79) 
        {
            System.out.println(a);
            Thread.sleep(200);
            a++;
 
        }
    }
} 

Execute the above program first and then read this explanation -

The Ascii value of '*' is 42, so when you say System.out.println(a) in your while loop, you will get a star in the first line of your output which is fine, but then in the very next line of your while by saying a++ you are actually incrementing the ascii value internally. So now the value has become 43 and 43 represents a '+' which will be the o/p on the second line. Then again the while loop proceeds executing a++ thus making a = 44 which represents a ',' which is the output on your third line..and so on..Thats why your program outputs a series of characters followed by infinite lines of ?....

Hope you see the output of the above program first, understand it and then change your logic accordingly. We will keep giving you pointers wherever you need help.

[colinNeedsJavaHelp]

Ok so I got the program how it should be the only problem is that it doesnt produce the right output. When ran it prompts the user "How many lines?" But then when you put in a number it doesnt do anything, the cursor just moves to the next line and stays there. I have to turn this in tomorrow morning so if anyone knows what is going wrong I would appreciate the help. I also changed it to a for loop. The part where the mistake is has to be in the loop but I can't for the life of me figure it out.

 
import java.io.*;
import java.util.*;
 
public class MagicPrinter
{
public static void main(String[] args)
throws java.io.IOException
{
String inputString;
int num1;
int a =1;
int i;
int j;
 
//for the input stream
InputStreamReader isr = new InputStreamReader(System.in);
 
//needed to use ReadLine()
BufferedReader br = new BufferedReader(isr);
 
System.out.print("How many lines? ");
inputString = br.readLine();
 
num1 = Integer.parseInt(br.readLine());
num1 = 0;
for(i =1; i<num1; i++){
for(j = i; j<0;j--){   
System.out.print("*");
}
System.out.println();
}
}
}
 

[colinNeedsJavaHelp]

Actually instead of assigning "*" to a character I just used it in the output.

[r035198x]

Actually instead of assigning "*" to a character I just used it in the output.

num1 = Integer.parseInt(br.readLine());

That is fine so far. Maybe you want to add error handling (what if the user enters something not a number?)

num1 = 0;

Now that's very bad. You have just thrown away the value that we want. Remove that line

for(i =1; i<num1; i++){
for(j = i; j<0;j--){
System.out.print("*");
}

You don't need two for statements.

You just need one for statement that prints the stars like this

 String stars = "*"; 
for(int i = 0;i < num1;i++) {
    //print stars
    //print a space
    //add a star to stars use the + operator
    //skip a line
}
 

[colinNeedsJavaHelp]

That is fine so far. Maybe you want to add error handling (what if the user enters something not a number?)


Now that's very bad. You have just thrown away the value that we want. Remove that line




You don't need two for statements.

You just need one for statement that prints the stars like this

 String stars = "*"; 
for(int i = 0;i < num1;i++) {
    //print stars
    //print a space
    //add a star to stars use the + operator
    //skip a line
}
 

I took out num1 = 0;

But I have to keep the 2 "for" statements so it does a loop. How can I get it to work? I cannot find anything wrong

[r035198x]

I took out num1 = 0;

But I have to keep the 2 "for" statements so it does a loop. How can I get it to work? I cannot find anything wrong

Ah so you're online. Won't be long before you complete this now.

No you do not need 2 for loops
Just fill in the codes for lines marked // in the for that I gave you

 
for(int i = 0;i < num1;i++) {
//print stars
//print a space
//add a star to stars use the + operator
//skip a line
}
 

e.g
for //print stars, replace with

System.out.println(stars);

[r035198x]

Ah so you're online. Won't be long before you complete this now.

No you do not need 2 for loops
Just fill in the codes for lines marked // in the for that I gave you

 
for(int i = 0;i < num1;i++) {
//print stars
//print a space
//add a star to stars use the + operator
//skip a line
}
 

e.g
for //print stars, replace with

System.out.println(stars);

Just a point of correction

 
for(int i = 0;i < num1;i++) {
//print stars
//add a space to stars use the + operator
//add a star to stars use the + operator
//skip a line
}