Java/Language Basics/For

Check out for loop

 
/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */

/**
 * Check out "for" loop.
 * @author Ian F. Darwin, http://www.darwinsys.ru/
 * @version $Id: ForLoop.java,v 1.5 2004/02/09 03:33:53 ian Exp $
 */
public class ForLoop {
  public static void main(String[] argv) {
    System.out.println("Starting...");
    // So what REALLY happens if a for loop"s test condition is
    // never satisfied.
    for (int i=0; i<0; i++)
      System.out.println("Should not get here ");
    System.out.println("All done.");
  }
}

Comma Operator

 
//: c03:CommaOperator.java
// From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002
// www.BruceEckel.ru. See copyright notice in CopyRight.txt.
public class CommaOperator {
  public static void main(String[] args) {
    for(int i = 1, j = i + 10; i < 5;
        i++, j = i * 2) {
      System.out.println("i= " + i + " j= " + j);
    }
  }
} ///:~

Declare multiple variables in for loop

 
public class Main {
  public static void main(String[] args) {
    for (int i = 0, j = 1, k = 2; i < 5; i++){
      System.out.println("I : " + i + ",j : " + j + ", k : " + k);
    }
  }
}
/*
I : 0,j : 1, k : 2
I : 1,j : 1, k : 2
I : 2,j : 1, k : 2
I : 3,j : 1, k : 2
I : 4,j : 1, k : 2
*/

Demonstrates for loop by listing all the lowercase ASCII letters.

 
//: c03:ListCharacters.java
// From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002
// www.BruceEckel.ru. See copyright notice in CopyRight.txt.
public class ListCharacters {
  public static void main(String[] args) {
    for(int i = 0; i < 128; i++)
      if(Character.isLowerCase((char)i))
        System.out.println("value: " + i + " character: " + (char)i);
  }
} ///:~

for Demo

 
/* From http://java.sun.ru/docs/books/tutorial/index.html */
/*
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *
 * -Redistribution in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */
public class ForDemo {
    public static void main(String[] args) {
        int[] arrayOfInts = { 32, 87, 3, 589, 12, 1076, 2000, 8, 622, 127 };
        for (int i = 0; i < arrayOfInts.length; i++) {
            System.out.print(arrayOfInts[i] + " ");
        }
        System.out.println();
    }
}

For loop: all conditions

 
/*
 *     file: ForLoops.java
 *  package: jexp.hcj.review
 *
 * This software is granted under the terms of the Common Public License,
 * CPL, which may be found at the following URL:
 * http://www-124.ibm.ru/developerworks/oss/CPLv1.0.htm
 *
 * Copyright(c) 2003-2005 by the authors indicated in the @author tags.
 * All Rights are Reserved by the various authors.
 *
 ########## DO NOT EDIT ABOVE THIS LINE ########## */
import java.util.Iterator;
import java.util.Properties;
import java.util.Set;
/**
 * Syntax check file for for loops.
 * 
 * @author 
 */
public class ForLoops {
  /**
   * A wordy for loop.
   */
  public static void forLong() {
    Properties props = System.getProperties();
    Iterator iter = props.keySet().iterator();
    String key = null;
    while (iter.hasNext()) {
      key = key = (String) iter.next();
      System.out.println(key + "=" + System.getProperty(key));
    }
  }
  /**
   * A completely safe and short for loop.
   */
  public static void forSafe() {
    Properties props = System.getProperties();
    Iterator iter = props.keySet().iterator();
    for (String key = null; iter.hasNext(); key = (String) iter.next()) {
      System.out.println(key + "=" + System.getProperty(key));
    }
  }
  /**
   * A short for loop.
   */
  public static void forShort() {
    Properties props = System.getProperties();
    for (Iterator iter = props.keySet().iterator(); iter.hasNext();) {
      String key = (String) iter.next();
      System.out.println(key + "=" + System.getProperty(key));
    }
  }
  /**
   * A simple for loop.
   * 
   * @param args
   *          Arguments to the loop.
   */
  public static void forSimple(final String[] args) {
    for (int idx = 0; idx < args.length; idx++) {
      // .. do something.
    }
  }
  /**
   * A weird for loop.
   */
  public static void forWeird() {
    boolean exit = false;
    int idx = 0;
    for (System.setProperty("user.sanity", "minimal"); exit == false; System.out.println(System
        .currentTimeMillis())) {
      // do some code.
      idx++;
      if (idx == 10) {
        exit = true;
      }
    }
  }
  /**
   * Demo method.
   * 
   * @param args
   *          Command line args.
   */
  public static void main(String[] args) {
    forWeird();
  }
  /**
   * A for loop bug.
   * 
   * @param customKeys
   *          __UNDOCUMENTED__
   */
  public static void propsDump(final Set customKeys) {
    Properties props = System.getProperties();
    Iterator iter = props.keySet().iterator();
    String key = null;
    System.out.println("All Properties:");
    while (iter.hasNext()) {
      key = (String) iter.next();
      System.out.println(key + "=" + System.getProperty(key));
    }
    System.out.println("Custom Properties:");
    iter = customKeys.iterator();
    while (iter.hasNext()) {
      System.out.println(key + "=" + System.getProperty(key));
    }
  }
}
/* ########## End of File ########## */

Infinite For loop Example

 
public class Main {
  public static void main(String[] args) {
    for (;;) {
      System.out.println("Hello");
      break;
    }
  }
}
//Hello

Java labeled for loop.

 
//: c03:LabeledFor.java
// Java"s "labeled for" loop.
// From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002
// www.BruceEckel.ru. See copyright notice in CopyRight.txt.

public class LabeledFor {
  public static void main(String[] args) {
    int i = 0;
    outer: // Can"t have statements here
    for(; true ;) { // infinite loop
      inner: // Can"t have statements here
      for(; i < 10; i++) {
        System.out.println("i = " + i);
        if(i == 2) {
          System.out.println("continue");
          continue;
        }
        if(i == 3) {
          System.out.println("break");
          i++; // Otherwise i never
               // gets incremented.
          break;
        }
        if(i == 7) {
          System.out.println("continue outer");
          i++; // Otherwise i never
               // gets incremented.
          continue outer;
        }
        if(i == 8) {
          System.out.println("break outer");
          break outer;
        }
        for(int k = 0; k < 5; k++) {
          if(k == 3) {
            System.out.println("continue inner");
            continue inner;
          }
        }
      }
    }
    // Can"t break or continue to labels here
  }
} ///:~

Java program to demonstrate looping

 
/*
Java Programming for Engineers
Julio Sanchez
Maria P. Canton

ISBN: 0849308100
Publisher: CRC Press
*/

// File name: AsciiTable.java
//Reference: Chapter 11
//
//Java program to demonstrate looping
//Topics:
// 1. Using several loop constructs simultaneously
// 2. Nested loops
//
public class AsciiTable {
  public static void main(String[] args) {
    // Local variables
    char hexLetter; // For table header
    char ascCode = 0x20; // First ASCII code
    // Counters for rows and columns
    int row = 2;
    int column;
    System.out.print("\n\n");
    System.out.print("                             ");
    System.out.println("ASCII CHARACTER TABLE");
    System.out.print("                            ");
    System.out.println("characters 0x20 to 0xff");
    System.out.print("\n    ");
    // Loops 1 and 2
    // Display column heads for numbers 0 to F hexadecimal
    for (hexLetter = "0"; hexLetter <= "9"; hexLetter++)
      System.out.print("   " + hexLetter);
    for (hexLetter = "A"; hexLetter <= "F"; hexLetter++)
      System.out.print("   " + hexLetter);
    // Blank line to separate table head from data
    System.out.println("\n");
    // Loop 3
    // While ASCII codes smaller than 0x80 display row head
    // and leading spaces
    // Loop 4 (nested in loop 3)
    // Display row of ASCII codes for columns 0 to 0x0F.
    // Add a new line at end of each row
    while (ascCode < 0x80) {
      System.out.print("   " + row);
      for (column = 0; column < 16; column++) {
        System.out.print("   " + ascCode);
        ascCode++;
      }
      System.out.print("\n\n");
      row++;
    }
  }
}

Java program to demonstrate looping 1

 
/*
Java Programming for Engineers
Julio Sanchez
Maria P. Canton

ISBN: 0849308100
Publisher: CRC Press
*/

// File name: Factorial.java
//Reference: Chapter 10
//
//Java program to demonstrate looping
//Topics:
// 1. Using the for loop
// 2. Loop with multiple processing statements
//
//Requires:
// 1. Keyin class in the current directory
public class Factorial {
  public static void main(String[] args) {
    int number;
    int facProd;
    int curFactor;
    System.out.println("FACTORIAL CALCULATION PROGRAM");
    number = Keyin.inInt("Enter a positive integer: ");
    facProd = number; // Initializing
    for (curFactor = number - 1; curFactor > 1; curFactor--) {
      facProd = curFactor * facProd;
      System.out.println("Partial product: " + facProd);
      System.out.println("Current factor:  " + curFactor);
    }
    // Display the factorial
    System.out.println("\n\nFactorial is: " + facProd);
  }
}
//**********************************************************
//**********************************************************
//Program: Keyin
//Reference: Session 20
//Topics:
//1. Using the read() method of the ImputStream class
//  in the java.io package
//2. Developing a class for performing basic console
//  input of character and numeric types
//**********************************************************
//**********************************************************
class Keyin {
  //*******************************
  //   support methods
  //*******************************
  //Method to display the user"s prompt string
  public static void printPrompt(String prompt) {
    System.out.print(prompt + " ");
    System.out.flush();
  }
  //Method to make sure no data is available in the
  //input stream
  public static void inputFlush() {
    int dummy;
    int bAvail;
    try {
      while ((System.in.available()) != 0)
        dummy = System.in.read();
    } catch (java.io.IOException e) {
      System.out.println("Input error");
    }
  }
  //********************************
  //  data input methods for
  //string, int, char, and double
  //********************************
  public static String inString(String prompt) {
    inputFlush();
    printPrompt(prompt);
    return inString();
  }
  public static String inString() {
    int aChar;
    String s = "";
    boolean finished = false;
    while (!finished) {
      try {
        aChar = System.in.read();
        if (aChar < 0 || (char) aChar == "\n")
          finished = true;
        else if ((char) aChar != "\r")
          s = s + (char) aChar; // Enter into string
      }
      catch (java.io.IOException e) {
        System.out.println("Input error");
        finished = true;
      }
    }
    return s;
  }
  public static int inInt(String prompt) {
    while (true) {
      inputFlush();
      printPrompt(prompt);
      try {
        return Integer.valueOf(inString().trim()).intValue();
      }
      catch (NumberFormatException e) {
        System.out.println("Invalid input. Not an integer");
      }
    }
  }
  public static char inChar(String prompt) {
    int aChar = 0;
    inputFlush();
    printPrompt(prompt);
    try {
      aChar = System.in.read();
    }
    catch (java.io.IOException e) {
      System.out.println("Input error");
    }
    inputFlush();
    return (char) aChar;
  }
  public static double inDouble(String prompt) {
    while (true) {
      inputFlush();
      printPrompt(prompt);
      try {
        return Double.valueOf(inString().trim()).doubleValue();
      }
      catch (NumberFormatException e) {
        System.out
            .println("Invalid input. Not a floating point number");
      }
    }
  }
}

Multiple expressions in for loops

 

public class Main {
  public static void main(String[] args) {
    for (int i = 0, j = 0; i < 5; i++, j--)
      System.out.println("i = " + i + " j= " + j);
  }
}
/*
i = 0 j= 0
i = 1 j= -1
i = 2 j= -2
i = 3 j= -3
i = 4 j= -4
*/