import java.util.regex.*; public class Delimiter { public static void main(String[] args) { String str = "Here is [some] text"; System.out.println("str: " + str); Matcher m = Pattern.compile("\\[([^)]+)\\]").matcher(str); while(m.find()) { System.out.println(m.group(1)); } } }
$ java Delimiter str: Here is [some] text some
import java.util.*; public class ListProperties { public static void main(String[] args) { Properties props = System.getProperties(); props.list(System.out); } }
$ java ListProperties -- listing properties -- java.runtime.name=Java(TM) SE Runtime Environment sun.boot.library.path=/jdk7/jre/lib/amd64 java.vm.version=24.45-b08 java.vm.vendor=Oracle Corporation java.vendor.url=http://java.oracle.com/ path.separator=: java.vm.name=Java HotSpot(TM) 64-Bit Server VM file.encoding.pkg=sun.io user.country=US sun.java.launcher=SUN_STANDARD sun.os.patch.level=unknown java.vm.specification.name=Java Virtual Machine Specification user.dir=/tmp/src java.runtime.version=1.7.0_45-b34 java.awt.graphicsenv=sun.awt.X11GraphicsEnvironment java.endorsed.dirs=/jdk7/jre/lib/endorsed os.arch=amd64 java.io.tmpdir=/tmp line.separator= java.vm.specification.vendor=Oracle Corporation os.name=Linux sun.jnu.encoding=UTF-8 java.library.path=/usr/java/packages/lib/amd64:/usr/lib... java.specification.name=Java Platform API Specification java.class.version=51.0 sun.management.compiler=HotSpot 64-Bit Tiered Compilers os.version=3.2.0-67-generic user.home=/home/dennis user.timezone= java.awt.printerjob=sun.print.PSPrinterJob file.encoding=UTF-8 java.specification.version=1.7 user.name=dennis java.class.path=. java.vm.specification.version=1.7 sun.arch.data.model=64 java.home=/jdk7/jre sun.java.command=ListProperties java.specification.vendor=Oracle Corporation user.language=en awt.toolkit=sun.awt.X11.XToolkit java.vm.info=mixed mode java.version=1.7.0_45 java.ext.dirs=/jdk7/jre/lib/ext:/usr/java/packages/... sun.boot.class.path=/jdk7/jre/lib/resources.jar:/jdk7/jre... java.vendor=Oracle Corporation file.separator=/ java.vendor.url.bug=http://bugreport.sun.com/bugreport/ sun.cpu.endian=little sun.io.unicode.encoding=UnicodeLittle sun.cpu.isalist=
public class ClassLocationTest { public static void main(String[] args) { ClassLocation cl = new ClassLocation(); System.out.println(cl.getClass().getProtectionDomain().getCodeSource().getLocation()); } } class ClassLocation { }
$ javac -d /tmp/classes ClassLocationTest.java $ java -cp /tmp/classes ClassLocationTest file:/tmp/classes/
public class Animal { public void speak(){ } } class Cat extends Animal{ @Override public void speak(){ System.out.println("meow"); } }
class MyClass implements MyInterfaceOne,MyInterfaceTwo { public void methodOne(){ System.out.println("inside methodOne()"); } public void methodTwo(){ System.out.println("inside methodTwo()"); } } interface MyInterfaceOne { void methodOne(); } interface MyInterfaceTwo { void methodTwo(); } public class MyClassTest { public static void main(String[] args) { MyClass mc = new MyClass(); mc.methodOne(); mc.methodTwo(); } }
$ java MyClassTest inside methodOne() inside methodTwo()
java.applet java.awt java.awt.color java.awt.datatransfer java.awt.dnd java.awt.event java.awt.font java.awt.geom java.awt.im java.awt.im.spi java.awt.image java.awt.image.renderable java.awt.print java.beans java.beans.beancontext java.io java.lang java.lang.annotation java.lang.instrument java.lang.invoke java.lang.management java.lang.ref java.lang.reflect java.math java.net java.nio java.nio.channels java.nio.channels.spi java.nio.charset java.nio.charset.spi java.nio.file java.nio.file.attribute java.nio.file.spi java.rmi java.rmi.activation java.rmi.dgc java.rmi.registry java.rmi.server java.security java.security.acl java.security.cert java.security.interfaces java.security.spec java.sql java.text java.text.spi java.util java.util.concurrent java.util.concurrent.atomic java.util.concurrent.locks java.util.jar java.util.logging java.util.prefs java.util.regex java.util.spi java.util.zip javax.accessibility javax.activation javax.activity javax.annotation javax.annotation.processing javax.crypto javax.crypto.interfaces javax.crypto.spec javax.imageio javax.imageio.event javax.imageio.metadata javax.imageio.plugins.bmp javax.imageio.plugins.jpeg javax.imageio.spi javax.imageio.stream javax.jws javax.jws.soap javax.lang.model javax.lang.model.element javax.lang.model.type javax.lang.model.util javax.management javax.management.loading javax.management.modelmbean javax.management.monitor javax.management.openmbean javax.management.relation javax.management.remote javax.management.remote.rmi javax.management.timer javax.naming javax.naming.directory javax.naming.event javax.naming.ldap javax.naming.spi javax.net javax.net.ssl javax.print javax.print.attribute javax.print.attribute.standard javax.print.event javax.rmi javax.rmi.CORBA javax.rmi.ssl javax.script javax.security.auth javax.security.auth.callback javax.security.auth.kerberos javax.security.auth.login javax.security.auth.spi javax.security.auth.x500 javax.security.cert javax.security.sasl javax.sound.midi javax.sound.midi.spi javax.sound.sampled javax.sound.sampled.spi javax.sql javax.sql.rowset javax.sql.rowset.serial javax.sql.rowset.spi javax.swing javax.swing.border javax.swing.colorchooser javax.swing.event javax.swing.filechooser javax.swing.plaf javax.swing.plaf.basic javax.swing.plaf.metal javax.swing.plaf.multi javax.swing.plaf.nimbus javax.swing.plaf.synth javax.swing.table javax.swing.text javax.swing.text.html javax.swing.text.html.parser javax.swing.text.rtf javax.swing.tree javax.swing.undo javax.tools javax.transaction javax.transaction.xa javax.xml javax.xml.bind javax.xml.bind.annotation javax.xml.bind.annotation.adapters javax.xml.bind.attachment javax.xml.bind.helpers javax.xml.bind.util javax.xml.crypto javax.xml.crypto.dom javax.xml.crypto.dsig javax.xml.crypto.dsig.dom javax.xml.crypto.dsig.keyinfo javax.xml.crypto.dsig.spec javax.xml.datatype javax.xml.namespace javax.xml.parsers javax.xml.soap javax.xml.stream javax.xml.stream.events javax.xml.stream.util javax.xml.transform javax.xml.transform.dom javax.xml.transform.sax javax.xml.transform.stax javax.xml.transform.stream javax.xml.validation javax.xml.ws javax.xml.ws.handler javax.xml.ws.handler.soap javax.xml.ws.http javax.xml.ws.soap javax.xml.ws.spi javax.xml.ws.spi.http javax.xml.ws.wsaddressing javax.xml.xpath org.ietf.jgss org.omg.CORBA org.omg.CORBA_2_3 org.omg.CORBA_2_3.portable org.omg.CORBA.DynAnyPackage org.omg.CORBA.ORBPackage org.omg.CORBA.portable org.omg.CORBA.TypeCodePackage org.omg.CosNaming org.omg.CosNaming.NamingContextExtPackage org.omg.CosNaming.NamingContextPackage org.omg.Dynamic org.omg.DynamicAny org.omg.DynamicAny.DynAnyFactoryPackage org.omg.DynamicAny.DynAnyPackage org.omg.IOP org.omg.IOP.CodecFactoryPackage org.omg.IOP.CodecPackage org.omg.Messaging org.omg.PortableInterceptor org.omg.PortableInterceptor.ORBInitInfoPackage org.omg.PortableServer org.omg.PortableServer.CurrentPackage org.omg.PortableServer.POAManagerPackage org.omg.PortableServer.POAPackage org.omg.PortableServer.portable org.omg.PortableServer.ServantLocatorPackage org.omg.SendingContext org.omg.stub.java.rmi org.w3c.dom org.w3c.dom.bootstrap org.w3c.dom.events org.w3c.dom.ls org.xml.sax org.xml.sax.ext org.xml.sax.helpers
import static java.lang.Math.PI; import static java.lang.Integer.MAX_VALUE; public class StaticImportStatements { public static void main(String[] args) { System.out.println("PI: " + PI); System.out.println("Int max: " + MAX_VALUE); } }
$ java StaticImportStatements PI: 3.141592653589793 Int max: 2147483647
public class Copyright { public static void main(String[] args) { System.out.println("Copyright \u00a9 2014"); } }
$ java Copyright Copyright © 2014
public class PrintPercentSign { public static void main(String[] args) { System.out.printf("4 out of 10 is %d%% \n", 40); } }
$ java PrintPercentSign 4 out of 10 is 40%
import java.util.Scanner; public class TipCalculator { public static void main(String [] args) { double rate1 = 0.1; double rate2 = 0.15; double rate3 = 0.2; Scanner keyboard = new Scanner(System.in); System.out.print("Enter the purchase price: "); double total = keyboard.nextDouble(); System.out.printf("10%%: %.2f \n", (total*rate1)); System.out.printf("15%%: %.2f \n", (total*rate2)); System.out.printf("20%%: %.2f \n", (total*rate3)); } }
$ java TipCalculator Enter the purchase price: 29.99 10%: 3.00 15%: 4.50 20%: 6.00
import java.util.Random; public class RandomNumbers { public static void main(String[] args) { Random r = new Random(); int x; // generate random number between 10 and 20 int low=10; int high=20; x = r.nextInt(high-low)+low; System.out.println(x); } }
$ java RandomNumbers 15
import java.util.*; import java.text.*; public class TimerExample { static int x=0; static int timerx = x; public static void main(String[] args) { class MyTimeTask extends TimerTask { public void run() { if(timerx != x) { timerx=x; System.out.println("x changed: " + x); } System.out.println("x: " + x); } } Timer timer = new Timer(true); timer.schedule(new MyTimeTask(), 0, 3000); for (int i=0;i<10;i++){ x=i; try { Thread.sleep(8000); } catch (InterruptedException e) { } } } }
$ java TimerExample x: 0 x: 0 x: 0 x changed: 1 x: 1 x: 1 x: 1 x changed: 2 x: 2 x: 2 x changed: 3 x: 3 x: 3 x: 3 x changed: 4 x: 4 x: 4 x: 4 x changed: 5 x: 5 x: 5 x changed: 6 x: 6 x: 6 x: 6 x changed: 7 x: 7 x: 7 x: 7 x changed: 8 x: 8 x: 8 x changed: 9 x: 9 x: 9 x: 9
import java.util.*; public class SumOfEvensPositions { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter a number: "); String str = sc.nextLine(); try { Integer.parseInt(str); int total=0; for(int i=1;i<str.length();i=i+2){ System.out.println("Pos " + (i+1) + " : " + str.charAt(i)); total = total + Character.getNumericValue(str.charAt(i)); } System.out.println("Total: " + total); } catch(NumberFormatException e) { System.out.println("Invalid number"); } } }
$ java SumOfEvensPositions Enter a number: 29664 Pos 2 : 9 Pos 4 : 6 Total: 15
import java.util.*; public class HighLowGuessingGame { public static void main(String[] args) { Random random = new Random(); Scanner scanner = new Scanner(System.in); int number = random.nextInt(100)+1; int guess = -1; int count=0; while(guess!=number){ Beginning: while (guess!=number) { count=count+1; System.out.print("Enter a number between 1 and 100: "); guess = scanner.nextInt(); while (guess<number) { System.out.println("Too low, please try again"); break Beginning; } while (guess>number) { System.out.println("Too high, please try again"); break Beginning; } } } System.out.println("Correct, the number was " + number); System.out.println("It took you " + count + " trys."); } }
$ java HighLowGuessingGame Enter a number between 1 and 100: 50 Too low, please try again Enter a number between 1 and 100: 75 Too high, please try again Enter a number between 1 and 100: 63 Too low, please try again Enter a number between 1 and 100: 69 Too low, please try again Enter a number between 1 and 100: 72 Too high, please try again Enter a number between 1 and 100: 70 Correct, the number was 70 It took you 6 trys.
import java.util.Scanner; public class Cookies { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter how many cookies you ate: "); int cookieCount = sc.nextInt(); int servingSize = 40/10; int caloriesPerCookie = 300/servingSize; int totalCalories = cookieCount * caloriesPerCookie; System.out.println("Total calories consumed: " + totalCalories); } }
$ java Cookies Enter how many cookies you ate: 6 Total calories consumed: 450
import java.util.Scanner; public class NthPrime { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter n to compute the nth prime number: "); int nth = sc.nextInt(); int num, count, i; num=1; count=0; while (count < nth){ num=num+1; for (i = 2; i <= num; i++){ if (num % i == 0) { break; } } if ( i == num){ count = count+1; } } System.out.println("Value of nth prime: " + num); } }
$ java NthPrime Enter n to compute the nth prime number: 10 Value of nth prime: 29
public class TestSums { public static void main(String[] args) { int vars[] = new int[args.length]; for(int n=0;n<vars.length;n++){ try { vars[n]= Integer.parseInt(args[n]); } catch (NumberFormatException e) { System.out.println(args[n] + " is no a number."); } } for(int i=0;i<vars.length;i++){ for(int j=i+1;j<vars.length;j++){ System.out.print(vars[i] + "," + vars[j] + ": " ); System.out.println(sumIsPowerOfTwo(vars[i],vars[j])); } } } static boolean sumIsPowerOfTwo(int x, int y) { int z = x + y; return ((z & (z -1)) == 0); } }
$ java TestSums 2 4 6 8 2,4: false 2,6: true 2,8: false 4,6: false 4,8: false 6,8: false
public class Example { public static void main(String[] args) { int integer1 = 33; int integer2 = 7; int quotient = integer1 / integer2; int remainder = integer1 % integer2; int product = quotient * remainder; double average = (double)(quotient + remainder) / 2; System.out.println("Quotient: " + quotient); System.out.println("Remainder: " + remainder); System.out.println("Product: " + product); System.out.println("Average: " + average); } }
$ java Example Quotient: 4 Remainder: 5 Product: 20 Average: 4.5
import java.util.Scanner; public class TemperatureTest { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter Fahrenheit temperature: "); double ftemp = sc.nextDouble(); Temperature temp = new Temperature(ftemp); System.out.println("The temperature in Fahrenheit is " + temp.getFahrenheit()); System.out.println("The temperature in Celsius is " + temp.getCelsius()); System.out.println("The temperature in Kelvin is " + temp.getKelvin()); } } class Temperature { double ftemp; Temperature(double ftemp) { this.ftemp = ftemp; } double getFahrenheit(){ return ftemp; } double getCelsius(){ return ((double)5/9*(ftemp-32)); } double getKelvin(){ return (((double)5/9*(ftemp-32))+273); } }
$ java TemperatureTest Enter Fahrenheit temperature: -40 The temperature in Fahrenheit is -40.0 The temperature in Celsius is -40.0 The temperature in Kelvin is 233.0
public class Ranges { public static void main(String[] args) { // double min / max. System.out.println(" Double.MAX_VALUE: " + Double.MAX_VALUE); System.out.println(" Double.MIN_NORMAL: " + Double.MIN_NORMAL); // float min / max. System.out.println(" Float.MAX_VALUE: " + Float.MAX_VALUE); System.out.println(" Float.MIN_VALUE: " + Float.MIN_VALUE); } }
$ java Ranges Double.MAX_VALUE: 1.7976931348623157E308 Double.MIN_NORMAL: 2.2250738585072014E-308 Float.MAX_VALUE: 3.4028235E38 Float.MIN_VALUE: 1.4E-45
import java.util.*; public class ShuffleArrays { public static void main(String[] args) { Random r = new Random(); int array1[] = new int[r.nextInt(10)]; int array2[] = new int[r.nextInt(10)]; int array3[] = new int[array1.length + array2.length]; System.out.println("array1 size: " + array1.length); System.out.println("array2 size: " + array2.length); System.out.println("array3 size: " + array3.length); // populate array1 & array2 with random numbers for(int i=0;i<array1.length;i++){ array1[i]=r.nextInt(100); } for(int i=0;i<array2.length;i++){ array2[i]=r.nextInt(100); } // populate array3 with contents of array1 & array2 for(int i=0;i<array1.length;i++){ array3[i]=array1[i]; } for(int i=0;i<array2.length;i++){ array3[i+array1.length]=array2[i]; } System.out.println("array1: " + Arrays.toString(array1)); System.out.println("array2: " + Arrays.toString(array2)); System.out.println("array3: " + Arrays.toString(array3)); // shuffle array3 int temp; int swapindex; System.out.println("array3: shuffling"); for(int i=0;i<array3.length;i++){ temp=array3[i]; swapindex=r.nextInt(array3.length); array3[i]=array3[swapindex]; array3[swapindex]=temp; } System.out.println("array3: " + Arrays.toString(array3)); } }
$ java ShuffleArrays array1 size: 9 array2 size: 6 array3 size: 15 array1: [82, 52, 72, 62, 77, 65, 39, 28, 97] array2: [27, 0, 12, 78, 35, 14] array3: [82, 52, 72, 62, 77, 65, 39, 28, 97, 27, 0, 12, 78, 35, 14] array3: shuffling array3: [72, 39, 77, 82, 27, 78, 62, 97, 12, 0, 35, 65, 14, 52, 28]
import java.util.Scanner; public class Seconds { public static void main(String[] args) { Scanner sc = new Scanner(System.in); System.out.print("Enter the number of seconds: "); int input = sc.nextInt(); int hours = input / 3600; int minutes = (input % 3600) / 60; int seconds = (input % 3600) % 60; System.out.println("Hours: " + hours); System.out.println("Minutes: " + minutes); System.out.println("Seconds: " + seconds); } }
$ java Seconds Enter the number of seconds: 50391 Hours: 13 Minutes: 59 Seconds: 51