Package edu.princeton.cs.algs4

Class BTree<Key extends Comparable<Key>,​Value>

  • public class BTree<Key extends Comparable<Key>,​Value>
extends Object
    The BTree class represents an ordered symbol table of generic key-value pairs. It supports the put, get, contains, size, and is-empty methods. A symbol table implements the associative array 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 Map, this class uses the convention that values cannot be null—setting the value associated with a key to null is equivalent to deleting the key from the symbol table.

    This implementation uses a B-tree. It requires that the key type implements the Comparable interface and calls the compareTo() and method to compare two keys. It does not call either equals() or hashCode(). The get, put, and contains operations each make logm(n) probes in the worst case, where n is the number of key-value pairs and m is the branching factor. The size, and is-empty operations take constant time. Construction takes constant time.

    For additional documentation, see Section 6.2 of Algorithms, 4th Edition by Robert Sedgewick and Kevin Wayne.

    • Constructor Summary

      Constructors 
      Constructor Description
      BTree()
      Initializes an empty B-tree.

    • Constructor Detail

      • BTree

        public BTree()
        Initializes an empty B-tree.

    • Method Detail

      • isEmpty

        public boolean isEmpty()
        Returns true if this symbol table is empty.
        Returns:
        true if this symbol table is empty; false otherwise

      • size

        public int size()
        Returns the number of key-value pairs in this symbol table.
        Returns:
        the number of key-value pairs in this symbol table

      • height

        public int height()
        Returns the height of this B-tree (for debugging).
        Returns:
        the height of this B-tree

      • get

        public Value get​(Key key)
        Returns the value associated with the given key.
        Parameters:
        key - the key
        Returns:
        the value associated with the given key if the key is in the symbol table and null if the key is not in the symbol table
        Throws:
        IllegalArgumentException - if key is null

      • put

        public void put​(Key key,
                Value val)
        Inserts the key-value pair into the symbol table, overwriting the old value with the new value if the key is already in the symbol table. If the value is null, this effectively deletes the key from the symbol table.
        Parameters:
        key - the key
        val - the value
        Throws:
        IllegalArgumentException - if key is null

      • toString

        public String toString()
        Returns a string representation of this B-tree (for debugging).
        Overrides:
        toString in class Object
        Returns:
        a string representation of this B-tree.

      • main

        public static void main​(String[] args)
        Unit tests the BTree data type.
        Parameters:
        args - the command-line arguments