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'.T his 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'.T his 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(integer s) not strings.

You can simply say:

DataInputStream input = new DataInputStream(System.in);
		
System.out.println("How many lines you have to print?");
int [B]num1 [/B] = 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(integer s) not strings.

You can simply say:

DataInputStream input = new DataInputStream(System.in);
		
System.out.println("How many lines you have to print?");
int [B]num1 [/B] = 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.prin tln(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]

for/while loop

What is the difference?