Learning JAVA (with basic standalone code snippets)

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/**
 * HelloWorld.java
 *  The first program anyone should write in any language.
 */
public class HelloWorld {
 
  public static void main(String[] args) {
    System.out.println("Hello World");
  }
}
 
 
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/**
 * HelloFromCommandLine.java
 *  The second program anyone should write in any language. 
 *  This teaches you to accept input to your program as parameters 
 *  at run-time. The Program will say your name when you provide 
 *  an input.
 *  args[0] is the program name
 *  args[1] is the first parameter
 *  args[n] is the Nth parameter
 * EXAMPLE
 *   Call the program as follows (from the command-line):
 *     java HelloFromCommandLine Michael
 *   For special characters and spaces, enclose the parameter "in quotes":
 *     java HelloFromCommandLine "Michael Jackson"
 */
public class HelloFromCommandLine {
  public static void main(String[] args) {
    String name = "";
    //check that the input is valid (i.e. not missing or empty space)
    if (args[1] == null || args[1].equals("")) {
      System.exit(1);
    }
    else {
      name = args[1];
    }
    System.out.println("Hello " + name);
  }
}
 
 
 
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/**
 * HelloFromConsole.java
 *  The first program anyone writes in any language.
 */
public class HelloFromConsole {
 
  public static void main(String[] args) {
    System.out.print("Please enter username: ");
    System.out.println(" ");
    ConsoleReader console = new ConsoleReader(System.in);   
    String username = console.readLine();
    System.out.println("Hello: " + username);
  }
}
 
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/**
 * Multiples.java
 *  Used to calculate N multiples of 2.
 */
public class Multiples() {
 
  public static void printMultsOf2(int multiples) {
    int runningTotal = 2;
    for (int i = 0; i < multiples; i++) {        
        System.out.print(runningTotal + " ");
        runningTotal += 2;
    }
  }
 
  public static void main(String[] args) {
    printMultsOf2(10);
  }
}
 
 
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/**
 * NumberToBinary.java
 *   Convert a Decimal Number to a Binary Number (i.e. "2" becomes "10").
 */
import java.io.*;
import java.lang.*;
 
public class NumberToBinary {
  public static void main(String[] args) throws IOException {
    BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
    System.out.println("Enter any number:");
    String sn = bf.readLine();
    int i = Integer.parseInt(sn);
    String s = Integer.toBinaryString(i);
    System.out.println("Binary number is:" + s);
  }
}
 
 
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/**
 * Grade.java
 *   Given a student score, calculate their Letter Grade.
 */
 
 
 
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/**
 * GPA.java
 *   Given a set of student scores, calculate their GPA.
 */
 
 
 
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/**
 * Lottery.java
 *   Generate lotto numbers and/or given a player's lotto
 *   ticket, check whether they are winners.
 */
 
 
 
 
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/**
 * ConnectToURL.java
 *  Connect to & display data from the web at a specific site's URL.
 */
import java.net.*;
import java.io.*;
 
public class ConnectToURL {
  public ConnectToURL() { }
 
  public static void main (String[] args) throws IOException {
    try {
           URL url = new URL("http://www.bryancopeland.com");   
           BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
           String str;
 
           while ((str = in.readLine()) != null) {
              System.out.println(str);
           }
 
           in.close();
     } 
     catch (MalformedURLException e) {} 
     catch (IOException e) {}
  }
}
 
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//                     THE END                          //
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