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Java Standard Streams All the programming languages provide support for standard I/O where the user's program can take input from a keyboard and then produce an output on the computer screen. If you are aware of C or C++ programming languages, then you must be aware of three standard devices STDIN, STDOUT and STDERR. Similarly, Java provides the following three standard streams: Standard Input: This is used to feed the data to user's program and usually a keyboard is used as standard input stream and represented as System.in. Standard Output: This is used to output the data produced by the user's program and usually a computer screen is used for standard output stream and represented as System.out. Standard Error: This is used to output the error data produced by the user's program and usually a computer screen is used for standard error stream and represented as System.err. Following is a simple program, which creates InputStreamReader to read standard input stream until the user types a "q": import java.io.*; public class ReadConsole { public static void main(String args[]) throws IOException { InputStreamReader cin = null; } } try { cin = new InputStreamReader(System.in); System.out.println("Enter characters, 'q' to quit."); char c; do { c = (char) cin.read(); System.out.print(c); } while(c != 'q'); }finally { if (cin != null) { cin.close(); } } 247
Java Let's keep the above code in ReadConsole.java file and try to compile and execute it as shown in the following program. This program continues to raed and output the same character until we press 'q': $javac ReadConsole.java $java ReadConsole Enter characters, 'q' to quit. 1 1 e e q q Reading and Writing Files As described earlier, a stream can be defined as a sequence of data. The InputStream is used to read data from a source and the OutputStream is used for writing data to a destination. Here is a hierarchy of classes to deal with Input and Output streams. 248
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Java About the Tutorial Java is a h
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Java 5. Java - Basic Datatypes ....
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Java Java - String Buffer delete()
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Java File Class ...................
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Java The Dictionary Class .........
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Java - Basics
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Java Distributed: Java is designe
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2. Java - Environment Setup Java In
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3. Java - Basic Syntax Java When we
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Java Java Identifiers All Java comp
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Java class const continue default d
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4. Java - Objects & Classes Java Ja
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Java Each time a new object is crea
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Java This will produce the followin
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Java Example This example explains
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Java Import Statements In Java if a
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Java Now, compile both the classes
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Java Example: short s = 10000, sho
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Java Prefix 0 is used to indicate o
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6. Java - Variable Types Java A var
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7. Java - Modifier Types Java Modif
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Java Protected Access Modifier - Pr
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Java private static void addInstanc
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Java The Abstract Modifier Abstract
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Java Example public class MyRunnabl
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8. Java - Basic Operators Java Java
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Java // Check the difference in d++
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Java Example The following program
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Java Example The following simple e
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Java 9 &= Bitwise AND assignment op
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Java c /= a = 1 c %= a = 5 c = 2 =
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Java Precedence of Java Operators O
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Java While Loop in Java A while loo
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Java Syntax The syntax of a for loo
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Java } This will produce the follow
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Java Expression: This evaluates to
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Java nested if statements You can u
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Java Flow Diagram Example public cl
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Java } } This will produce the foll
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Java A switch statement can have a
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Java What is Next? In the next chap
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Java 17 sqrt() Returns the square r
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Java // Returns double primitive da
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Java Example public class Test{ pub
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Java Java - toString() Method Descr
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Java } } System.out.println(Math.fl
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Java } } System.out.println(Math.ri
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Java Return Value This method retu
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12. Java - Character Class Java Nor
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Java Character Methods Following is
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Java Example public class Test { }
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Java Example public class Test{ } p
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Java The StringBuilder class was in
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Java Parameters Here is the detail
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Java 11 void setLength(int newLengt
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Java Using String's static format()
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Java 15 int hashCode() Returns a ha
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Java 35 boolean startsWith(String p
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Java Java - String compareTo(Object
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Java } } result = str3.compareTo( s
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Java Example public class Test { pu
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Java Parameters Here is the detail
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Java } } }catch( Exception ex){ } S
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Java Example import java.io.*; publ
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Java fromIndex -- the index to sta
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Java Return Value Example This met
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Java System.out.println(Str1.region
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Java Java - String replace() Method
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Java Java - String replaceFirst() M
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Java } } System.out.println(retval)
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Java } } System.out.println(retval)
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Java } } System.out.println(Str.sta
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Java Syntax Here is the syntax of t
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Java Java - String toLowerCase() Me
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Java Java - String toString() Metho
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Java Syntax Here is the syntax of t
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Java valueOf(char[] data, int
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Page 208 and 209: Java The above statement does two t
Page 210 and 211: Java The foreach Loops JDK 1.5 intr
Page 212 and 213: Java public static void fill(int[]
Page 214 and 215: Java 5 int compareTo(Object obj) Op
Page 216 and 217: Java Simple DateFormat Format Codes
Page 218 and 219: Java } } // display time and date u
Page 220 and 221: Java I Two-digit hour (with leading
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Page 224 and 225: Java 5 GregorianCalendar(Locale aLo
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Page 232 and 233: Java re? Matches 0 or 1 occurrence
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Page 238 and 239: Java } } System.out.println("lookin
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Page 262 and 263: Java This method reads upto len num
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Page 290 and 291: Java Catching Exceptions A method c
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Java 297
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Java Java - Object Oriented 299
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Java Copy and paste the following p
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Java Differentiating the Members If
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Java Invoking Superclass Constructo
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Java Now, if we consider the IS-A r
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22. Java - Overriding Java In the p
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Java } } b.bark(); This will produc
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23. Java - Polymorphism Java Polymo
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Java } public void setAddress(Strin
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Java mailCheck() on e is quite diff
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Java { System.out.println("Construc
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Java Inheriting the Abstract Class
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Java You have to place the abstr
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Java public void setAge( int newAge
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26. Java - Interfaces Java An inter
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Java A class uses the implements ke
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Java The Hockey interface has four
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Java Following package example cont
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Java What happens if the Employee c
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Java Like the .java source files, t
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28. Java - Data Structures Java The
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Java 10 void flip(int startIndex, i
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Java // set some bits for(int i=0;
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Java This constructor accepts an ar
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Java 17 Object get(int index) Retur
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Java 36 void setSize(int newSize) S
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Java static void showpop(Stack st)
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Java boolean isEmpty( ) 3 Returns t
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Java Object put(Object k, Object v)
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Java Hashtable(int size, float fill
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Java Apart from the methods defined
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Java The Collection Interfaces The
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Java boolean equals(Object obj) 6 7
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Java } } //HashMap Map m1 = new Has
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Java Example The above interface ha
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Java Example Set has its implementa
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Java 7 8 int hashCode( ) Returns th
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Java } } Vector dayNames = new Vect
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Java 10 AbstractMap Implements most
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Java Object get(int index) 10 Retur
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Java // remove elements from the li
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Java 6 Object clone() Returns a sha
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Java } } // display the array list
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Java 5 6 7 8 boolean isEmpty() Retu
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Java LinkedHashSet hs = new LinkedH
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Java 11 12 13 Object last() Returns
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Java 3 4 5 boolean containsKey(Obje
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Java 14 15 Object remove(Object key
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Java } }; Thread t = new Thread(run
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Java // Put elements to the map lhm
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Java Apart from the methods inherit
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Java } } } System.out.println(); //
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Java 4 Vector(Collection c) Creates
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Java 24 int lastIndexOf(Object elem
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Java v.addElement(new Integer(4));
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Java 4 Enumeration keys( ) Returns
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Java 13 int size( ) Returns the num
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Java boolean containsKey(Object key
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Java Set states; String str; capita
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Java boolean equals(Object bitSet)
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Java System.out.println("Initial pa
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Java 5 static void fill(List list,
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Java 30 31 32 33 34 35 36 37 static
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Java How to Use an Iterator ? Often
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Java public class Example{ public s
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Java } } System.out.printf("Seriali
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Java Returns the port of the URL. 5
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Java URLConnections Class Methods T
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Java } { } try { URL url = new URL(
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Java ServerSocket Class Methods The
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Java public Socket() 5 Creates an u
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Java { String serverName = args[0];
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Java } { System.out.println("Socket
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Java // Get system properties Prope
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Java // Assuming you are sending em
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Java try{ // Create a default MimeM
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34. Java - Multithreading Java Java
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Java void start( ); Example Here is
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Java Step 1 You will need to overri
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Java Thread: Thread-2, 2 Thread: Th
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Java Example The following ThreadCl
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Java Multithreading Example without
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Java Counter --- 3 Counter --- 2 Co
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Java } synchronized (Lock2) { Syste
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Java } } } } synchronized (Lock2) {
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Java Thread: Thread-2, 7 Suspending
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Java Example HTML applet Tag
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Java Not valid in base, br, frame,
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Java onresize onstorage onundo onun
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Java Media Events Following tags ha
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Java public void mouseExited(MouseE
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36. Java - Documentation Comments J
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Java @exception Adds a Throws subhe
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Java /** * This is the main method
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