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Java: Processing Input and Parameters - Command Line Input and StringTokenizer, Study notes of Java Programming

North Carolina State University (NCSU)Java Programming

An overview of processing input and parameters in java, focusing on reading command line input using bufferedreader and inputstreamreader, and the use of stringtokenizer for breaking apart strings. It includes examples and explanations of various methods and techniques.

Typology: Study notes

Pre 2010

Uploaded on 03/10/2009

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© 2005 Sarah E. Smith
Processing Input, Parameters, and
Return Values
CSC 116 – Section 002
March 14, 2005
© 2005 Sarah E. Smith
Review of Command Line Input
• Use BufferedReader and InputStreamReader
classes to read input
• Use System.in to specify that input comes
from standard input
• Syntax:
BufferedReader console =
new BufferedReader(new InputStreamReader(System.in));
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Download Java: Processing Input and Parameters - Command Line Input and StringTokenizer and more Study notes Java Programming in PDF only on Docsity!

© 2005 Sarah E. Smith

Processing Input, Parameters, and

Return Values

CSC 116 – Section 002 March 14, 2005

© 2005 Sarah E. Smith

Review of Command Line Input

  • Use BufferedReader and InputStreamReader

classes to read input

  • Use System.in to specify that input comes

from standard input

  • Syntax: BufferedReader console = new BufferedReader(new InputStreamReader(System.in));

© 2005 Sarah E. Smith

Review of Command Line Input (2)

  • Use readLine() method to read a line from the terminal window
  • readLine() method may cause exceptions so wrap in a try-catch block try { String input = console.readLine(); } catch (IOException e) { System.out.println(“Error: “ + e); }

© 2005 Sarah E. Smith

Reading More Than One Line

  • You can use a BufferedReader to read a list

of input by using a while loop

© 2005 Sarah E. Smith

StringTokenizer Methods

  • StringTokenizer(String line)
    • Constructor
  • StringTokenizer(String line, String delimiters)
    • Tokenizes the String in line with the given delimiters
  • StringTokenizer.hasMoreTokens()
    • Returns true if the StringTokenizer has more tokens
  • StringTokenizer.countTokens()
    • Counts the remaining tokens
  • StringTokenizer.nextToken()
    • Returns a String that contains the next token

© 2005 Sarah E. Smith

StringTokenizer Example

StringTokenizer tokenizer = new

StringTokenizer(line);

int tokenCount = tokenizer.countTokens();

for (int i=0; i < tokenCount; i++) {

String token = tokenizer.nextToken();

System.out.println(token);

© 2005 Sarah E. Smith

StringTokenizer.countTokens()

  • Return the number of tokens that are left in

the Tokenizer

  • Whenever a token is retrieved from the list, it

is deleted!

  • Do not use this method in a for loop
    • Create a variable to store the total number of tokens before processing the tokens

© 2005 Sarah E. Smith

Formal and Actual Parameters

  • Formal Parameters – include this and all declared parameters (the data types and names in the parenthesis)
  • Actual Parameters – values that you supply a method
  • Actual parameters copy their values to the formal parameters memory locations - this gets the location in memory of the calling object - The parameter gets the value passed into it

© 2005 Sarah E. Smith

Execution Flow Example

amt=yConvert.fromD(200);

Memory

public double fromDollar(double d) { double amt, fee; fee = er – fr; amt = d * fee; return amt; }

amt

fee

amt

d 200.

© 2005 Sarah E. Smith

Execution Flow Example

amt=yConvert.fromD(200);

Memory

public double fromDollar(double d) { double amt, fee; fee = er – fr; amt = d * fee; return amt; }

amt

fee 124.

amt 24846.

d 200.

© 2005 Sarah E. Smith

Execution Flow Example

amt=yConvert.fromD(200);

Memory

public double fromDollar(double d) { double amt, fee; fee = er – fr; amt = d * fee; return amt; }

amt 24846.

© 2005 Sarah E. Smith

Execution Flow Example (2)

int x = 10; int y = 20; tester.myMethod(x,y);

Memory

public void myMethod (int one, double two) { one = 25; two = 35.4; }

y 20

x 10

© 2005 Sarah E. Smith

Execution Flow Example (2)

int x = 10; int y = 20; tester.myMethod(x,y);

Memory

public void myMethod (int one, double two) { one = 25; two = 35.4; }

y 20

x 10

© 2005 Sarah E. Smith

References

  • Jason Schwarz’s Lecture 14 and 15 slides:

http://courses.ncsu.edu/csc116/

  • Example of execution flow from Chapter 4.

in Wu p 172 and 174