# 数据结构之栈的Java实现

## 基本算法

1．进栈（PUSH）算法①若TOP≥n时，则给出溢出信息，作出错处理（进栈前首先检查栈是否已满，满则溢出；不满则作②）；②置TOP=TOP+1（栈指针加1，指向进栈地址）；③S(TOP)=X，结束（X为新进栈的元素）；2．退栈（POP）算法①若TOP≤0，则给出下溢信息，作出错处理(退栈前先检查是否已为空栈， 空则下溢；不空则作②)；②X=S(TOP)，（退栈后的元素赋给X）：③TOP=TOP-1，结束（栈指针减1，指向栈顶）。

## 实现

`/****************************************************************************** * Compilation: javac Stack.java * Execution: java Stack < input.txt * Dependencies: StdIn.java StdOut.java * * A generic stack, implemented using a singly-linked list. * Each stack element is of type Item. * * This version uses a static nested class Node (to save 8 bytes per * Node), whereas the version in the textbook uses a non-static nested * class (for simplicity). * * % more tobe.txt * to be or not to - be - - that - - - is * * % java Stack < tobe.txt * to be not that or be (2 left on stack) * ******************************************************************************/import java.util.Iterator;import java.util.NoSuchElementException;/** * The <tt>Stack</tt> class represents a last-in-first-out (LIFO) stack of generic items. * It supports the usual <em>push</em> and <em>pop</em> operations, along with methods * for peeking at the top item, testing if the stack is empty, and iterating through * the items in LIFO order. * <p> * This implementation uses a singly-linked list with a static nested class for * linked-list nodes. See {@link LinkedStack} for the version from the * textbook that uses a non-static nested class. * The <em>push</em>, <em>pop</em>, <em>peek</em>, <em>size</em>, and <em>is-empty</em> * operations all take constant time in the worst case. * <p> * For additional documentation, * see <a href="http://algs4.cs.princeton.edu/13stacks">Section 1.3</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * * @author Robert Sedgewick * @author Kevin Wayne * * @param <Item> the generic type of an item in this stack */public class Stack<Item> implements Iterable<Item> { private Node<Item> first; // top of stack private int N; // size of the stack // helper linked list class private static class Node<Item> { private Item item; private Node<Item> next; } /** * Initializes an empty stack. */ public Stack() { first = null; N = 0; } /** * Returns true if this stack is empty. * * @return true if this stack is empty; false otherwise */ public boolean isEmpty() { return first == null; } /** * Returns the number of items in this stack. * * @return the number of items in this stack */ public int size() { return N; } /** * Adds the item to this stack. * * @param item the item to add */ public void push(Item item) { Node<Item> oldfirst = first; first = new Node<Item>(); first.item = item; first.next = oldfirst; N++; } /** * Removes and returns the item most recently added to this stack. * * @return the item most recently added * @throws NoSuchElementException if this stack is empty */ public Item pop() { if (isEmpty()) throw new NoSuchElementException("Stack underflow"); Item item = first.item; // save item to return first = first.next; // delete first node N--; return item; // return the saved item } /** * Returns (but does not remove) the item most recently added to this stack. * * @return the item most recently added to this stack * @throws NoSuchElementException if this stack is empty */ public Item peek() { if (isEmpty()) throw new NoSuchElementException("Stack underflow"); return first.item; } /** * Returns a string representation of this stack. * * @return the sequence of items in this stack in LIFO order, separated by spaces */ public String toString() { StringBuilder s = new StringBuilder(); for (Item item : this) s.append(item + " "); return s.toString(); } /** * Returns an iterator to this stack that iterates through the items in LIFO order. * * @return an iterator to this stack that iterates through the items in LIFO order */ public Iterator<Item> iterator() { return new ListIterator<Item>(first); } // an iterator, doesn't implement remove() since it's optional private class ListIterator<Item> implements Iterator<Item> { private Node<Item> current; public ListIterator(Node<Item> first) { current = first; } public boolean hasNext() { return current != null; } public void remove() { throw new UnsupportedOperationException(); } public Item next() { if (!hasNext()) throw new NoSuchElementException(); Item item = current.item; current = current.next; return item; } } /** * Unit tests the <tt>Stack</tt> data type. */ public static void main(String[] args) { Stack<String> s = new Stack<String>(); while (!StdIn.isEmpty()) { String item = StdIn.readString(); if (!item.equals("-")) s.push(item); else if (!s.isEmpty()) StdOut.print(s.pop() + " "); } StdOut.println("(" + s.size() + " left on stack)"); }}`

`/****************************************************************************** * Compilation: javac StdIn.java * Execution: java StdIn (interactive test of basic functionality) * Dependencies: none * * Reads in data of various types from standard input. * ******************************************************************************/import java.util.ArrayList;import java.util.InputMismatchException;import java.util.Locale;import java.util.NoSuchElementException;import java.util.Scanner;import java.util.regex.Pattern;/** * The <tt>StdIn</tt> class provides static methods for reading strings * and numbers from standard input. * These functions fall into one of four categories: * <p> * <ul> * <li>those for reading individual tokens from standard input, one at a time, * and converting each to a number, string, or boolean * <li>those for reading characters from standard input, one at a time * <li>those for reading lines from standard input, one at a time * <li>those for reading a sequence of values of the same type from standard input, * and returning the values in an array * </ul> * <p> * Generally, it is best not to mix functions from the different * categories in the same program. * <p> * <b>Reading tokens from standard input one at a time, * and converting to numbers and strings.</b> * You can use the following methods to read numbers, strings, and booleans * from standard input: * <ul> * <li> {@link #readInt()} * <li> {@link #readDouble()} * <li> {@link #readString()} * <li> {@link #readBoolean()} * <li> {@link #readShort()} * <li> {@link #readLong()} * <li> {@link #readFloat()} * <li> {@link #readByte()} * </ul> * <p> * Each method skips over any input that is whitespace. Then, it reads * the next token and attempts to convert it into a value of the specified * type. If it succeeds, it returns that value; otherwise, it * throws a {@link InputMismatchException}. * <p> * <em>Whitespace</em> includes spaces, tabs, and newlines; the full definition * is inherited from {@link Character#isWhitespace(char)}. * A <em>token</em> is a maximal sequence of non-whitespace characters. * The precise rules for describing which tokens can be converted to * integers and floating-point numbers are inherited from * <a href = "http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#number-syntax">Scanner</a>, * using the locale {@link Locale#US}; the rules * for floating-point numbers are slightly different * from those in {@link Double#valueOf(String)}, * but unlikely to be of concern to most programmers. * <p> * <b>Reading characters from standard input, one at a time.</b> * You can use the following two methods to read characters from standard input: * <ul> * <li> {@link #hasNextChar()} * <li> {@link #readChar()} * </ul> * <p> * The first method returns true if standard input has more input (including whitespace). * The second method reads and returns the next character of input on standard * input (possibly a whitespace character). * <p> * As an example, the following code fragment reads characters from standard input, * one character at a time, and prints it to standard output. * <pre> * while (!StdIn.hasNextChar()) { * char c = StdIn.readChar(); * StdOut.print(c); * } * </pre> * <p> * <b>Reading lines from standard input, one at a time.</b> * You can use the following two methods to read lines from standard input: * <ul> * <li> {@link #hasNextLine()} * <li> {@link #readLine()} * </ul> * <p> * The first method returns true if standard input has more input (including whitespace). * The second method reads and returns the remaining portion of * the next line of input on standard input (possibly whitespace), * discarding the trailing line separator. * <p> * A <em>line separator</em> is defined to be one of the following strings: * {@code /n} (Linux), {@code /r} (old Macintosh), * {@code /r/n} (Windows), * <code>/u2028</code>, <code>/u2029</code>, or <code>/u0085</code>. * <p> * As an example, the following code fragment reads text from standard input, * one line at a time, and prints it to standard output. * <pre> * while (!StdIn.hasNextLine()) { * String line = StdIn.readLine(); * StdOut.println(line); * } * </pre> * <p> * <b>Reading a sequence of values of the same type from standard input.</b> * You can use the following methods to read a sequence numbers, strings, * or booleans (all of the same type) from standard input: * <ul> * <li> {@link #readAllDoubles()} * <li> {@link #readAllInts()} * <li> {@link #readAllStrings()} * <li> {@link #readAllLines()} * <li> {@link #readAll()} * </ul> * <p> * The first three methods read of all of remaining token on standard input * and dconverts the tokens to values of * the specified type, as in the corresponding * {@code readDouble}, {@code readInt}, and {@code readString()} methods. * The {@code readAllLines()} method reads all remaining lines on standard * input and returns them as an array of strings. * The {@code readAll()} method reads all remaining input on standard * input and returns it as a string. * <p> * As an example, the following code fragment reads all of the remaining * tokens from standard input and returns them as an array of strings. * <pre> * String[] words = StdIn.readAllString(); * </pre> * <p> * <b>Differences with Scanner.</b> * {@code StdIn} and {@link Scanner} are both designed to parse * tokens and convert them to primitive types and strings. * Some of the main differences are summarized below: * <ul> * <li> {@code StdIn} is a set of static methods and reads * reads input from only standard input. It is suitable for use before * a programmer knows about objects. * See {@link In} for an object-oriented version that handles * input from files, URLs, * and sockets. * <li> {@code StdIn} uses whitespace as the delimiter between tokens. * <li> {@code StdIn} coerces the character-set encoding to UTF-8, * which is a standard character encoding for Unicode. * <li> {@code StdIn} coerces the locale to {@link Locale#US}, * for consistency with {@link StdOut}, {@link Double#parseDouble(String)}, * and floating-point literals. * <li> {@code StdIn} has convenient methods for reading a single * character; reading in sequences of integers, doubles, or strings; * and reading in all of the remaining input. * </ul> * <p> * Historical note: {@code StdIn} preceded {@code Scanner}; when * {@code Scanner} was introduced, this class was reimplemented to use it. * <p> * <b>Using standard input.</b> * Standard input is fundamental operating system abstraction, on Mac OS X, * Windows, and Linux. * The methods in {@code StdIn} are <em>blocking</em>, which means that they * will wait until you enter input on standard input. * If your program has a loop that repeats until standard input is empty, * you must signal that the input is finished. * To do so, depending on your operating system and IDE, * use either {@code <Ctrl-d>} or {@code <Ctrl-z>}, on its own line. * If you are redirecting standard input from a file, you will not need * to do anything to signal that the input is finished. * <p> * <b>Known bugs.</b> * Java's UTF-8 encoding does not recognize the optional * <a href = "http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4508058">byte-order mask</a>. * If the input begins with the optional byte-order mask, <tt>StdIn</tt> * will have an extra character <code>/uFEFF</code> at the beginning. * <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 David Pritchard * @author Robert Sedgewick * @author Kevin Wayne */public final class StdIn { /*** begin: section (1 of 2) of code duplicated from In to StdIn. */ // assume Unicode UTF-8 encoding private static final String CHARSET_NAME = "UTF-8"; // assume language = English, country = US for consistency with System.out. private static final Locale LOCALE = Locale.US; // the default token separator; we maintain the invariant that this value // is held by the scanner's delimiter between calls private static final Pattern WHITESPACE_PATTERN = Pattern.compile("//p{javaWhitespace}+"); // makes whitespace significant private static final Pattern EMPTY_PATTERN = Pattern.compile(""); // used to read the entire input private static final Pattern EVERYTHING_PATTERN = Pattern.compile("//A"); /*** end: section (1 of 2) of code duplicated from In to StdIn. */ private static Scanner scanner; // it doesn't make sense to instantiate this class private StdIn() { } //// begin: section (2 of 2) of code duplicated from In to StdIn, //// with all methods changed from "public" to "public static" /** * Returns true if standard input is empty (except possibly for whitespace). * Use this method to know whether the next call to {@link #readString()}, * {@link #readDouble()}, etc will succeed. * * @return <tt>true</tt> if standard input is empty (except possibly * for whitespace); <tt>false</tt> otherwise */ public static boolean isEmpty() { return !scanner.hasNext(); } /** * Returns true if standard input has a next line. * Use this method to know whether the * next call to {@link #readLine()} will succeed. * This method is functionally equivalent to {@link #hasNextChar()}. * * @return <tt>true</tt> if standard input is empty; * <tt>false</tt> otherwise */ public static boolean hasNextLine() { return scanner.hasNextLine(); } /** * Returns true if standard input has more inputy (including whitespace). * Use this method to know whether the next call to {@link #readChar()} will succeed. * This method is functionally equivalent to {@link #hasNextLine()}. * * @return <tt>true</tt> if standard input has more input (including whitespace); * <tt>false</tt> otherwise */ public static boolean hasNextChar() { scanner.useDelimiter(EMPTY_PATTERN); boolean result = scanner.hasNext(); scanner.useDelimiter(WHITESPACE_PATTERN); return result; } /** * Reads and returns the next line, excluding the line separator if present. * @return the next line, excluding the line separator if present */ public static String readLine() { String line; try { line = scanner.nextLine(); } catch (NoSuchElementException e) { line = null; } return line; } /** * Reads and returns the next character. * @return the next character */ public static char readChar() { scanner.useDelimiter(EMPTY_PATTERN); String ch = scanner.next(); assert ch.length() == 1 : "Internal (Std)In.readChar() error!" + " Please contact the authors."; scanner.useDelimiter(WHITESPACE_PATTERN); return ch.charAt(0); } /** * Reads and returns the remainder of the input, as a string. * @return the remainder of the input, as a string */ public static String readAll() { if (!scanner.hasNextLine()) return ""; String result = scanner.useDelimiter(EVERYTHING_PATTERN).next(); // not that important to reset delimeter, since now scanner is empty scanner.useDelimiter(WHITESPACE_PATTERN); // but let's do it anyway return result; } /** * Reads the next token and returns the <tt>String</tt>. * @return the next <tt>String</tt> */ public static String readString() { return scanner.next(); } /** * Reads the next token from standard input, parses it as an integer, and returns the integer. * @return the next integer on standard input * @throws InputMismatchException if the next token cannot be parsed as an <tt>int</tt> */ public static int readInt() { return scanner.nextInt(); } /** * Reads the next token from standard input, parses it as a double, and returns the double. * @return the next double on standard input * @throws InputMismatchException if the next token cannot be parsed as a <tt>double</tt> */ public static double readDouble() { return scanner.nextDouble(); } /** * Reads the next token from standard input, parses it as a float, and returns the float. * @return the next float on standard input * @throws InputMismatchException if the next token cannot be parsed as a <tt>float</tt> */ public static float readFloat() { return scanner.nextFloat(); } /** * Reads the next token from standard input, parses it as a long integer, and returns the long integer. * @return the next long integer on standard input * @throws InputMismatchException if the next token cannot be parsed as a <tt>long</tt> */ public static long readLong() { return scanner.nextLong(); } /** * Reads the next token from standard input, parses it as a short integer, and returns the short integer. * @return the next short integer on standard input * @throws InputMismatchException if the next token cannot be parsed as a <tt>short</tt> */ public static short readShort() { return scanner.nextShort(); } /** * Reads the next token from standard input, parses it as a byte, and returns the byte. * @return the next byte on standard input * @throws InputMismatchException if the next token cannot be parsed as a <tt>byte</tt> */ public static byte readByte() { return scanner.nextByte(); } /** * Reads the next token from standard input, parses it as a boolean, * and returns the boolean. * @return the next boolean on standard input * @throws InputMismatchException if the next token cannot be parsed as a <tt>boolean</tt>: * <tt>true</tt> or <tt>1</tt> for true, and <tt>false</tt> or <tt>0</tt> for false, * ignoring case */ public static boolean readBoolean() { String s = readString(); if (s.equalsIgnoreCase("true")) return true; if (s.equalsIgnoreCase("false")) return false; if (s.equals("1")) return true; if (s.equals("0")) return false; throw new InputMismatchException(); } /** * Reads all remaining tokens from standard input and returns them as an array of strings. * @return all remaining tokens on standard input, as an array of strings */ public static String[] readAllStrings() { // we could use readAll.trim().split(), but that's not consistent // because trim() uses characters 0x00..0x20 as whitespace String[] tokens = WHITESPACE_PATTERN.split(readAll()); if (tokens.length == 0 || tokens[0].length() > 0) return tokens; // don't include first token if it is leading whitespace String[] decapitokens = new String[tokens.length-1]; for (int i = 0; i < tokens.length - 1; i++) decapitokens[i] = tokens[i+1]; return decapitokens; } /** * Reads all remaining lines from standard input and returns them as an array of strings. * @return all remaining lines on standard input, as an array of strings */ public static String[] readAllLines() { ArrayList<String> lines = new ArrayList<String>(); while (hasNextLine()) { lines.add(readLine()); } return lines.toArray(new String[0]); } /** * Reads all remaining tokens from standard input, parses them as integers, and returns * them as an array of integers. * @return all remaining integers on standard input, as an array * @throws InputMismatchException if any token cannot be parsed as an <tt>int</tt> */ public static int[] readAllInts() { String[] fields = readAllStrings(); int[] vals = new int[fields.length]; for (int i = 0; i < fields.length; i++) vals[i] = Integer.parseInt(fields[i]); return vals; } /** * Reads all remaining tokens from standard input, parses them as doubles, and returns * them as an array of doubles. * @return all remaining doubles on standard input, as an array * @throws InputMismatchException if any token cannot be parsed as a <tt>double</tt> */ public static double[] readAllDoubles() { String[] fields = readAllStrings(); double[] vals = new double[fields.length]; for (int i = 0; i < fields.length; i++) vals[i] = Double.parseDouble(fields[i]); return vals; } //// end: section (2 of 2) of code duplicated from In to StdIn // do this once when StdIn is initialized static { resync(); } /** * If StdIn changes, use this to reinitialize the scanner. */ private static void resync() { setScanner(new Scanner(new java.io.BufferedInputStream(System.in), CHARSET_NAME)); } private static void setScanner(Scanner scanner) { StdIn.scanner = scanner; StdIn.scanner.useLocale(LOCALE); } /** * Reads all remaining tokens, parses them as integers, and returns * them as an array of integers. * @return all remaining integers, as an array * @throws InputMismatchException if any token cannot be parsed as an <tt>int</tt> * @deprecated Replaced by {@link #readAllInts()}. */ public static int[] readInts() { return readAllInts(); } /** * Reads all remaining tokens, parses them as doubles, and returns * them as an array of doubles. * @return all remaining doubles, as an array * @throws InputMismatchException if any token cannot be parsed as a <tt>double</tt> * @deprecated Replaced by {@link #readAllDoubles()}. */ public static double[] readDoubles() { return readAllDoubles(); } /** * Reads all remaining tokens and returns them as an array of strings. * @return all remaining tokens, as an array of strings * @deprecated Replaced by {@link #readAllStrings()}. */ public static String[] readStrings() { return readAllStrings(); } /** * Interactive test of basic functionality. */ public static void main(String[] args) { StdOut.print("Type a string: "); String s = StdIn.readString(); StdOut.println("Your string was: " + s); StdOut.println(); StdOut.print("Type an int: "); int a = StdIn.readInt(); StdOut.println("Your int was: " + a); StdOut.println(); StdOut.print("Type a boolean: "); boolean b = StdIn.readBoolean(); StdOut.println("Your boolean was: " + b); StdOut.println(); StdOut.print("Type a double: "); double c = StdIn.readDouble(); StdOut.println("Your double was: " + c); StdOut.println(); }}`

`/****************************************************************************** * 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); }}`