Below is the syntax highlighted version of ST.java.
/****************************************************************************** * Compilation: javac ST.java * Execution: java ST < input.txt * Dependencies: StdIn.java StdOut.java * Data files: https://algs4.cs.princeton.edu/35applications/tinyST.txt * * Sorted symbol table implementation using a java.util.TreeMap. * Does not allow duplicates. * ******************************************************************************/ package edu.princeton.cs.algs4; import java.util.Iterator; import java.util.NoSuchElementException; import java.util.TreeMap; /** * The {@code ST} class represents an ordered symbol table of generic * key-value pairs. * It supports the usual <em>put</em>, <em>get</em>, <em>contains</em>, * <em>delete</em>, <em>size</em>, and <em>is-empty</em> methods. * It also provides ordered methods for finding the <em>minimum</em>, * <em>maximum</em>, <em>floor</em>, and <em>ceiling</em>. * It also provides a <em>keys</em> method for iterating over all of the keys. * A symbol table implements the <em>associative array</em> abstraction: * when associating a value with a key that is already in the symbol table, * the convention is to replace the old value with the new value. * Unlike {@link java.util.Map}, this class uses the convention that * values cannot be {@code null}—setting the * value associated with a key to {@code null} is equivalent to deleting the key * from the symbol table. * <p> * It requires that * the key type implements the {@code Comparable} interface and calls the * {@code compareTo()} and method to compare two keys. It does not call either * {@code equals()} or {@code hashCode()}. * <p> * This implementation uses a <em>red-black BST</em>. * The <em>put</em>, <em>get</em>, <em>contains</em>, <em>remove</em>, * <em>minimum</em>, <em>maximum</em>, <em>ceiling</em>, and <em>floor</em> * operations each take Θ(log <em>n</em>) time in the worst case, * where <em>n</em> is the number of key-value pairs in the symbol table. * The <em>size</em> and <em>is-empty</em> operations take Θ(1) time. * Construction takes Θ(1) time. * <p> * For additional documentation, see * <a href="https://algs4.cs.princeton.edu/35applications">Section 3.5</a> of * <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne. * * @author Robert Sedgewick * @author Kevin Wayne * * @param <Key> the generic type of keys in this symbol table * @param <Value> the generic type of values in this symbol table */ public class ST<Key extends Comparable<Key>, Value> implements Iterable<Key> { private TreeMap<Key, Value> st; /** * Initializes an empty symbol table. */ public ST() { st = new TreeMap<Key, Value>(); } /** * Returns the value associated with the given key in this symbol table. * * @param key the key * @return the value associated with the given key if the key is in this symbol table; * {@code null} if the key is not in this symbol table * @throws IllegalArgumentException if {@code key} is {@code null} */ public Value get(Key key) { if (key == null) throw new IllegalArgumentException("calls get() with null key"); return st.get(key); } /** * Inserts the specified key-value pair into the symbol table, overwriting the old * value with the new value if the symbol table already contains the specified key. * Deletes the specified key (and its associated value) from this symbol table * if the specified value is {@code null}. * * @param key the key * @param val the value * @throws IllegalArgumentException if {@code key} is {@code null} */ public void put(Key key, Value val) { if (key == null) throw new IllegalArgumentException("calls put() with null key"); if (val == null) st.remove(key); else st.put(key, val); } /** * Removes the specified key and its associated value from this symbol table * (if the key is in this symbol table). * This is equivalent to {@code remove()}, but we plan to deprecate {@code delete()}. * * @param key the key * @throws IllegalArgumentException if {@code key} is {@code null} */ public void delete(Key key) { if (key == null) throw new IllegalArgumentException("calls delete() with null key"); st.remove(key); } /** * Removes the specified key and its associated value from this symbol table * (if the key is in this symbol table). * This is equivalent to {@code delete()}, but we plan to deprecate {@code delete()}. * * @param key the key * @throws IllegalArgumentException if {@code key} is {@code null} */ public void remove(Key key) { if (key == null) throw new IllegalArgumentException("calls remove() with null key"); st.remove(key); } /** * Returns true if this symbol table contain the given key. * * @param key the key * @return {@code true} if this symbol table contains {@code key} and * {@code false} otherwise * @throws IllegalArgumentException if {@code key} is {@code null} */ public boolean contains(Key key) { if (key == null) throw new IllegalArgumentException("calls contains() with null key"); return st.containsKey(key); } /** * Returns the number of key-value pairs in this symbol table. * * @return the number of key-value pairs in this symbol table */ public int size() { return st.size(); } /** * Returns true if this symbol table is empty. * * @return {@code true} if this symbol table is empty and {@code false} otherwise */ public boolean isEmpty() { return size() == 0; } /** * Returns all keys in this symbol table in ascending order, * as an {@code Iterable}. * <p> * To iterate over all of the keys in the symbol table named {@code st}, * use the foreach notation: {@code for (Key key : st.keys())}. * * @return all keys in this symbol table in ascending order */ public Iterable<Key> keys() { return st.keySet(); } /** * Returns all keys in this symbol table in ascending order. * To iterate over all of the keys in a symbol table named {@code st}, use the * foreach notation: {@code for (Key key : st)}. * <p> * This method is provided for backward compatibility with the version from * <em>Introduction to Programming in Java: An Interdisciplinary Approach.</em> * * @return all keys in this symbol table in ascending order * @deprecated Replaced by {@link #keys()}. */ @Deprecated public Iterator<Key> iterator() { return st.keySet().iterator(); } /** * Returns the smallest key in this symbol table. * * @return the smallest key in this symbol table * @throws NoSuchElementException if this symbol table is empty */ public Key min() { if (isEmpty()) throw new NoSuchElementException("calls min() with empty symbol table"); return st.firstKey(); } /** * Returns the largest key in this symbol table. * * @return the largest key in this symbol table * @throws NoSuchElementException if this symbol table is empty */ public Key max() { if (isEmpty()) throw new NoSuchElementException("calls max() with empty symbol table"); return st.lastKey(); } /** * Returns the smallest key in this symbol table greater than or equal to {@code key}. * * @param key the key * @return the smallest key in this symbol table greater than or equal to {@code key} * @throws NoSuchElementException if there is no such key * @throws IllegalArgumentException if {@code key} is {@code null} */ public Key ceiling(Key key) { if (key == null) throw new IllegalArgumentException("argument to ceiling() is null"); Key k = st.ceilingKey(key); if (k == null) throw new NoSuchElementException("argument to ceiling() is too large"); return k; } /** * Returns the largest key in this symbol table less than or equal to {@code key}. * * @param key the key * @return the largest key in this symbol table less than or equal to {@code key} * @throws NoSuchElementException if there is no such key * @throws IllegalArgumentException if {@code key} is {@code null} */ public Key floor(Key key) { if (key == null) throw new IllegalArgumentException("argument to floor() is null"); Key k = st.floorKey(key); if (k == null) throw new NoSuchElementException("argument to floor() is too small"); return k; } /** * Unit tests the {@code ST} data type. * * @param args the command-line arguments */ public static void main(String[] args) { ST<String, Integer> st = new ST<String, Integer>(); for (int i = 0; !StdIn.isEmpty(); i++) { String key = StdIn.readString(); st.put(key, i); } for (String s : st.keys()) StdOut.println(s + " " + st.get(s)); } } /****************************************************************************** * Copyright 2002-2022, Robert Sedgewick and Kevin Wayne. * * This file is part of algs4.jar, which accompanies the textbook * * Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne, * Addison-Wesley Professional, 2011, ISBN 0-321-57351-X. * http://algs4.cs.princeton.edu * * * algs4.jar is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * algs4.jar is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with algs4.jar. If not, see http://www.gnu.org/licenses. ******************************************************************************/