public class SymbolTable
extends java.lang.Object
addSymbol will always return the same string
 reference.
 
 The symbol table performs the same task as String.intern()
 with the following differences:
 
SymbolTable has two parameters that affect its
 performance: initial capacity and load factor.  The
 capacity is the number of buckets in the SymbolTable, and the
 initial capacity is simply the capacity at the time the SymbolTable
 is created.  Note that the SymbolTable is open: in the case of a "hash
 collision", a single bucket stores multiple entries, which must be searched
 sequentially.  The load factor is a measure of how full the SymbolTable
 is allowed to get before its capacity is automatically increased.
 When the number of entries in the SymbolTable exceeds the product of the load
 factor and the current capacity, the capacity is increased by calling the
 rehash method.Generally, the default load factor (.75) offers a good tradeoff between time and space costs. Higher values decrease the space overhead but increase the time cost to look up an entry (which is reflected in most SymbolTable operations, including addSymbol and containsSymbol).
 The initial capacity controls a tradeoff between wasted space and the
 need for rehash operations, which are time-consuming.
 No rehash operations will ever occur if the initial
 capacity is greater than the maximum number of entries the
 Hashtable will contain divided by its load factor.  However,
 setting the initial capacity too high can waste space.
 If many entries are to be made into a SymbolTable, 
 creating it with a sufficiently large capacity may allow the 
 entries to be inserted more efficiently than letting it perform 
 automatic rehashing as needed to grow the table. 
SymbolHash| Modifier and Type | Class and Description | 
|---|---|
| protected static class  | SymbolTable.EntryThis class is a symbol table entry. | 
| Modifier and Type | Field and Description | 
|---|---|
| protected SymbolTable.Entry[] | fBucketsBuckets. | 
| protected int | fCollisionThresholdA new hash function is selected and the table is rehashed when
 the number of keys in the bucket exceeds this threshold. | 
| protected int | fCountThe total number of entries in the hash table. | 
| protected int[] | fHashMultipliersArray of randomly selected hash function multipliers or  nullif the default String.hashCode() function should be used. | 
| protected float | fLoadFactorThe load factor for the SymbolTable. | 
| protected int | fTableSizeactual table size | 
| protected int | fThresholdThe table is rehashed when its size exceeds this threshold. | 
| protected static int | MAX_HASH_COLLISIONSMaximum hash collisions per bucket for a table with load factor == 1. | 
| protected static int | MULTIPLIERS_MASK | 
| protected static int | MULTIPLIERS_SIZE | 
| protected static int | TABLE_SIZEDefault table size. | 
| Constructor and Description | 
|---|
| SymbolTable()Constructs a new, empty SymbolTable with a default initial capacity (101)
 and load factor, which is 0.75. | 
| SymbolTable(int initialCapacity)Constructs a new, empty SymbolTable with the specified initial capacity
 and default load factor, which is 0.75. | 
| SymbolTable(int initialCapacity,
           float loadFactor)Constructs a new, empty SymbolTable with the specified initial 
 capacity and the specified load factor. | 
| Modifier and Type | Method and Description | 
|---|---|
| java.lang.String | addSymbol(char[] buffer,
         int offset,
         int length)Adds the specified symbol to the symbol table and returns a
 reference to the unique symbol. | 
| java.lang.String | addSymbol(java.lang.String symbol)Adds the specified symbol to the symbol table and returns a
 reference to the unique symbol. | 
| boolean | containsSymbol(char[] buffer,
              int offset,
              int length)Returns true if the symbol table already contains the specified
 symbol. | 
| boolean | containsSymbol(java.lang.String symbol)Returns true if the symbol table already contains the specified
 symbol. | 
| int | hash(char[] buffer,
    int offset,
    int length)Returns a hashcode value for the specified symbol information. | 
| int | hash(java.lang.String symbol)Returns a hashcode value for the specified symbol. | 
| protected void | rebalance()Randomly selects a new hash function and reorganizes this SymbolTable
 in order to more evenly distribute its entries across the table. | 
| protected void | rehash()Increases the capacity of and internally reorganizes this 
 SymbolTable, in order to accommodate and access its entries more 
 efficiently. | 
protected static final int TABLE_SIZE
protected static final int MAX_HASH_COLLISIONS
protected static final int MULTIPLIERS_SIZE
protected static final int MULTIPLIERS_MASK
protected SymbolTable.Entry[] fBuckets
protected int fTableSize
protected transient int fCount
protected int fThreshold
protected float fLoadFactor
protected final int fCollisionThreshold
protected int[] fHashMultipliers
null
 if the default String.hashCode() function should be used.public SymbolTable(int initialCapacity,
           float loadFactor)
initialCapacity - the initial capacity of the SymbolTable.loadFactor - the load factor of the SymbolTable.java.lang.IllegalArgumentException - if the initial capacity is less
             than zero, or if the load factor is nonpositive.public SymbolTable(int initialCapacity)
initialCapacity - the initial capacity of the hashtable.java.lang.IllegalArgumentException - if the initial capacity is less
            than zero.public SymbolTable()
public java.lang.String addSymbol(java.lang.String symbol)
symbol - The new symbol.public java.lang.String addSymbol(char[] buffer,
                         int offset,
                         int length)
buffer - The buffer containing the new symbol.offset - The offset into the buffer of the new symbol.length - The length of the new symbol in the buffer.public int hash(java.lang.String symbol)
hash(char[],int,int) method when called
 with the character array that comprises the symbol string.symbol - The symbol to hash.public int hash(char[] buffer,
       int offset,
       int length)
hash(String) method when called
 with the string object created from the symbol information.buffer - The character buffer containing the symbol.offset - The offset into the character buffer of the start
               of the symbol.length - The length of the symbol.protected void rehash()
protected void rebalance()
public boolean containsSymbol(java.lang.String symbol)
symbol - The symbol to look for.public boolean containsSymbol(char[] buffer,
                     int offset,
                     int length)
buffer - The buffer containing the symbol to look for.offset - The offset into the buffer.length - The length of the symbol in the buffer.Copyright © 1999-2022 The Apache Software Foundation. All Rights Reserved.