Java/Data Type/Convert from String

Convert from String to integer

   <source lang="java">
 

public class Main {

 public static void main(String[] args) throws Exception {
   String str = "25";
   int i = Integer.valueOf(str).intValue();
   // or
   i = Integer.parseInt(str);
 }

}

 </source>
   
  
 
  

Converting a String to a byte Number

   <source lang="java">

public class Main {

 public static void main(String[] argv) throws Exception {
   byte b = Byte.parseByte("123");
   System.out.println(b);
 }

}

 </source>
   
  
 
  

Converting a String to a int(integer) Number

   <source lang="java">

public class Main {

 public static void main(String[] argv) throws Exception {
   int i = Integer.parseInt("123");
   System.out.println(i);
 }

}

 </source>
   
  
 
  

Converting a String to a short Number

   <source lang="java">

public class Main {

 public static void main(String[] argv) throws Exception {
   short s = Short.parseShort("123");
   System.out.println(s);
 }

}

 </source>
   
  
 
  

Convert string to an integer or number

   <source lang="java">
 

public class Main {

 public static void main(String[] args) {
   String myNumber = "13";
   Integer number = Integer.parseInt(myNumber);
   System.out.println("My lucky number is: " + number);
   number = Integer.parseInt(myNumber, 16);
   System.out.println("My lucky number is: " + number);
   number = Integer.parseInt(myNumber, 8);
   System.out.println("My lucky number is: " + number);
 }

}

 </source>
   
  
 
  

Declaring Checked Exceptions

   <source lang="java">
 

public class Main {

 public void convertStringToInt() throws NumberFormatException {
   String s = "123";
   int number = Integer.parseInt(s);
 }

}

 </source>
   
  
 
  

Decode string to integer

   <source lang="java">
 

public class Main {

 public static void main(String[] args) {
   String decimal = "10"; // Decimal
   String hexa = "0XFF"; // Hexa
   String octal = "077"; // Octal
   Integer number = Integer.decode(decimal);
   System.out.println("String [" + decimal + "] = " + number);
   number = Integer.decode(hexa);
   System.out.println("String [" + hexa + "] = " + number);
   number = Integer.decode(octal);
   System.out.println("String [" + octal + "] = " + number);
 }

}

 </source>
   
  
 
  

Parse and format a number to decimal

   <source lang="java">
 

public class Main {

 public static void main(String[] argv) throws Exception {
   int i = Integer.parseInt("1023");
   String s = Integer.toString(i);
   System.out.println(s);
 }

}

 </source>
   
  
 
  

Parse and format a number to octal

   <source lang="java">
 

public class Main {

 public static void main(String[] argv) throws Exception {
   int i = Integer.parseInt("1000", 8);
   String s = Integer.toString(i, 8);
   System.out.println(s);
 }

}

 </source>
   
  
 
  

Parse and format to arbitrary radix <= Character.MAX_RADIX

   <source lang="java">
 

public class Main {

 public static void main(String[] argv) throws Exception {
   int radix = 32;
   int i = Integer.parseInt("vv", radix);
   String s = Integer.toString(i, radix);
 }

}

 </source>
   
  
 
  

Parse and format to hexadecimal

   <source lang="java">
 

public class Main {

 public static void main(String[] argv) throws Exception {
   int i = Integer.parseInt("3ff", 16);
   String s = Integer.toString(i, 16);
   System.out.println(s);
 }

}

 </source>
   
  
 
  

Parse a number using a NumberFormat

   <source lang="java">
 

import java.text.NumberFormat; import java.text.ParseException; /*

* Parse a number using a NumberFormat.
*/

public class NumFormatParse {

 //+
 /** A number to parse */
 public static final String input = "4096.251";
 //-
 /** The main (and only) method in this class. */
 public static void main(String[] av) { 
   //+
   NumberFormat defForm = NumberFormat.getInstance();
   try {
     Number d = defForm.parse(input);
     System.out.println(input + 
       " parses as " + d +
       " and formats as " + defForm.format(d));
   } catch (ParseException pe) {
     System.err.println(input + "not parseable!");
   }
   //-
 }

}

 </source>
   
  
 
  

Pass a string to the Integer class constructor and call the intValue()

   <source lang="java">
 

public class Main {

 public static void main(String[] argv) {
   String sValue = "5";
   try {
     int iValue = new Integer(sValue).intValue();
   } catch (NumberFormatException ex) {
     ex.printStackTrace();
   }
 }

}

 </source>
   
  
 
  

Validate if string is a number

   <source lang="java">
 

public class Main {

 public static boolean checkIfNumber(String in) {
   try {
     Integer.parseInt(in);
   } catch (NumberFormatException ex) {
     return false;
   }
   return true;
 }
 public static void main(String[] args) {
   System.out.println(checkIfNumber("ABC"));
   System.out.println(checkIfNumber("123123123123123"));
 }

}

 </source>
   
  
 
  

Value Of Demo

   <source lang="java">
 

/* 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 ValueOfDemo {

 public static void main(String[] args) {
   //this program requires two arguments on the command line
   if (args.length == 2) {
     //convert strings to numbers
     float a = Float.valueOf(args[0]).floatValue();
     float b = Float.valueOf(args[1]).floatValue();
     //do some arithmetic
     System.out.println("a + b = " + (a + b));
     System.out.println("a - b = " + (a - b));
     System.out.println("a * b = " + (a * b));
     System.out.println("a / b = " + (a / b));
     System.out.println("a % b = " + (a % b));
   } else {
     System.out
         .println("This program requires two command-line arguments.");
   }
 }

}

 </source>