Below is the syntax highlighted version of ST.java
from §4.4 Symbol Tables.
/****************************************************************************** * Compilation: javac ST.java * Execution: java ST * Dependencies: StdIn.java StdOut.java * * Sorted symbol table implementation using a java.util.TreeMap. * Does not allow duplicates. * * % java ST * ******************************************************************************/ 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>remove</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 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> * This implementation uses a balanced binary search tree. 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()}. * The <em>put</em>, <em>contains</em>, <em>remove</em>, <em>minimum</em>, * <em>maximum</em>, <em>ceiling</em>, and <em>floor</em> operations each take * logarithmic time in the worst case. * The <em>size</em>, and <em>is-empty</em> operations take constant time. * Construction takes constant time. * <p> * For additional documentation, * see <a href="https://introcs.cs.princeton.edu/44st">Section 4.4</a> of * <i>Computer Science: An Interdisciplinary Approach</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("called 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. * Removes 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("called 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). * * @param key the key * @throws IllegalArgumentException if {@code key} is {@code null} * @deprecated Replaced by {@link #remove(Comparable key)}. */ @Deprecated public void delete(Key key) { if (key == null) throw new IllegalArgumentException("called 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). * * @param key the key * @throws IllegalArgumentException if {@code key} is {@code null} */ public void remove(Key key) { if (key == null) throw new IllegalArgumentException("called 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("called 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. * <p> * To iterate over all 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 */ public Iterable<Key> keys() { return st.keySet(); } /** * Returns all the keys in this symbol table in ascending order. * To iterate over all the keys in a symbol table named {@code st}, * use the foreach notation: {@code for (Key key : st)}. * * @return an iterator to all the keys in this symbol table * @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("called 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("called 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("called ceiling() with null key"); Key k = st.ceilingKey(key); if (k == null) throw new NoSuchElementException("all keys are less than " + key); 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("called floor() with null key"); Key k = st.floorKey(key); if (k == null) throw new NoSuchElementException("all keys are greater than " + key); 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)); } }