StdOut.java

/******************************************************************************
 *  Compilation:  javac StdOut.java
 *  Execution:    java StdOut
 *  Dependencies: none
 *
 *  Writes data of various types to standard output.
 *
 ******************************************************************************/

import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.Locale;

/**
 *  This class provides methods for printing strings and numbers to standard output.
 *  <p>
 *  <b>Getting started.</b>
 *  To use this class, you must have <tt>StdOut.class</tt> in your
 *  Java classpath. If you used our autoinstaller, you should be all set.
 *  Otherwise, download
 *  <a href = "http://introcs.cs.princeton.edu/java/stdlib/StdOut.java">StdOut.java</a>
 *  and put a copy in your working directory.
 *  <p>
 *  Here is an example program that uses <code>StdOut</code>:
 *  <pre>
 *   public class TestStdOut {
 *       public static void main(String[] args) {
 *           int a = 17;
 *           int b = 23;
 *           int sum = a + b;
 *           StdOut.println("Hello, World");
 *           StdOut.printf("%d + %d = %d\n", a, b, sum);
 *       }
 *   }
 *  </pre>
 *  <p>
 *  <b>Differences with System.out.</b>
 *  The behavior of <code>StdOut</code> is similar to that of {@link System#out},
 *  but there are a few subtle differences:
 *  <ul>
 *  <li> <code>StdOut</code> coerces the character-set encoding to UTF-8,
 *       which is a standard character encoding for Unicode.
 *  <li> <code>StdOut</code> coerces the locale to {@link Locale#US},
 *       for consistency with {@link StdIn}, {@link Double#parseDouble(String)},
 *       and floating-point literals.
 *  <li> <code>StdOut</code> <em>flushes</em> standard output after each call to
 *       <code>print()</code> so that text will appear immediately in the terminal.
 *  </ul>
 *  <p>
 *  <b>Reference.</b>
 *  For additional documentation,
 *  see <a href="http://introcs.cs.princeton.edu/15inout">Section 1.5</a> of
 *  <em>Introduction to Programming in Java: An Interdisciplinary Approach</em>
 *  by Robert Sedgewick and Kevin Wayne.
 *
 *  @author Robert Sedgewick
 *  @author Kevin Wayne
 */
public final class StdOut {

    // force Unicode UTF-8 encoding; otherwise it's system dependent
    private static final String CHARSET_NAME = "UTF-8";

    // assume language = English, country = US for consistency with StdIn
    private static final Locale LOCALE = Locale.US;

    // send output here
    private static PrintWriter out;

    // this is called before invoking any methods
    static {
        try {
            out = new PrintWriter(new OutputStreamWriter(System.out, CHARSET_NAME), true);
        }
        catch (UnsupportedEncodingException e) {
            System.out.println(e);
        }
    }

    // don't instantiate
    private StdOut() { }

   /**
     * Closes standard output.
     */
    public static void close() {
        out.close();
    }

   /**
     * Terminates the current line by printing the line-separator string.
     */
    public static void println() {
        out.println();
    }

   /**
     * Prints an object to this output stream and then terminates the line.
     *
     * @param x the object to print
     */
    public static void println(Object x) {
        out.println(x);
    }

   /**
     * Prints a boolean to standard output and then terminates the line.
     *
     * @param x the boolean to print
     */
    public static void println(boolean x) {
        out.println(x);
    }

   /**
     * Prints a character to standard output and then terminates the line.
     *
     * @param x the character to print
     */
    public static void println(char x) {
        out.println(x);
    }

   /**
     * Prints a double to standard output and then terminates the line.
     *
     * @param x the double to print
     */
    public static void println(double x) {
        out.println(x);
    }

   /**
     * Prints an integer to standard output and then terminates the line.
     *
     * @param x the integer to print
     */
    public static void println(float x) {
        out.println(x);
    }

   /**
     * Prints an integer to standard output and then terminates the line.
     *
     * @param x the integer to print
     */
    public static void println(int x) {
        out.println(x);
    }

   /**
     * Prints a long to standard output and then terminates the line.
     *
     * @param x the long to print
     */
    public static void println(long x) {
        out.println(x);
    }

   /**
     * Prints a short integer to standard output and then terminates the line.
     *
     * @param x the short to print
     */
    public static void println(short x) {
        out.println(x);
    }

   /**
     * Prints a byte to standard output and then terminates the line.
     * <p>
     * To write binary data, see {@link BinaryStdOut}.
     *
     * @param x the byte to print
     */
    public static void println(byte x) {
        out.println(x);
    }

   /**
     * Flushes standard output.
     */
    public static void print() {
        out.flush();
    }

   /**
     * Prints an object to standard output and flushes standard output.
     * 
     * @param x the object to print
     */
    public static void print(Object x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints a boolean to standard output and flushes standard output.
     * 
     * @param x the boolean to print
     */
    public static void print(boolean x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints a character to standard output and flushes standard output.
     * 
     * @param x the character to print
     */
    public static void print(char x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints a double to standard output and flushes standard output.
     * 
     * @param x the double to print
     */
    public static void print(double x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints a float to standard output and flushes standard output.
     * 
     * @param x the float to print
     */
    public static void print(float x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints an integer to standard output and flushes standard output.
     * 
     * @param x the integer to print
     */
    public static void print(int x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints a long integer to standard output and flushes standard output.
     * 
     * @param x the long integer to print
     */
    public static void print(long x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints a short integer to standard output and flushes standard output.
     * 
     * @param x the short integer to print
     */
    public static void print(short x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints a byte to standard output and flushes standard output.
     *
     * @param x the byte to print
     */
    public static void print(byte x) {
        out.print(x);
        out.flush();
    }

   /**
     * Prints a formatted string to standard output, using the specified format
     * string and arguments, and then flushes standard output.
     *
     *
     * @param format the <a href = "http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax">format string</a>
     * @param args   the arguments accompanying the format string
     */
    public static void printf(String format, Object... args) {
        out.printf(LOCALE, format, args);
        out.flush();
    }

   /**
     * Prints a formatted string to standard output, using the locale and
     * the specified format string and arguments; then flushes standard output.
     *
     * @param locale the locale
     * @param format the <a href = "http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax">format string</a>
     * @param args   the arguments accompanying the format string
     */
    public static void printf(Locale locale, String format, Object... args) {
        out.printf(locale, format, args);
        out.flush();
    }

   /**
     * Unit tests some of the methods in <tt>StdOut</tt>.
     */
    public static void main(String[] args) {

        // write to stdout
        StdOut.println("Test");
        StdOut.println(17);
        StdOut.println(true);
        StdOut.printf("%.6f\n", 1.0/7.0);
    }

}