Package com.alibaba.fastjson2

Class SymbolTable

java.lang.Object
com.alibaba.fastjson2.SymbolTable
public final class SymbolTable extends Object
Symbol table for fast name lookup.

This class provides a way to efficiently map names (strings) to ordinals and vice versa. It uses FNV-1a hash algorithm for fast hashing and maintains sorted hash codes for binary search.

SymbolTable is designed to be immutable after construction, making it thread-safe.

Since:
2.0.58

  • Constructor Details

    • SymbolTable

      public SymbolTable(Class<?>... input)
      Create a symbol table from class names.
      Parameters:
      input - classes whose names will be added to the symbol table
      Since:
      2.0.58

    • SymbolTable

      public SymbolTable(String... input)
      Create a symbol table from string names.

      The names will be sorted and deduplicated. Each name is assigned a unique ordinal starting from 1. The ordinal 0 is reserved and means "not found".

      Parameters:
      input - names to be added to the symbol table

  • Method Details

    • size

      public int size()
      Get the number of names in this symbol table.
      Returns:
      the number of names

    • hashCode64

      public long hashCode64()
      Get the 64-bit hash code of this symbol table.

      The hash code is computed from all the names in the symbol table. It can be used to quickly compare if two symbol tables have the same content.

      Returns:
      the 64-bit hash code of this symbol table

    • getNameByHashCode

      public String getNameByHashCode(long hashCode)
      Get the name by its hash code.
      Parameters:
      hashCode - the FNV-1a 64-bit hash code of the name
      Returns:
      the name if found, null otherwise

    • getOrdinalByHashCode

      public int getOrdinalByHashCode(long hashCode)
      Get the ordinal of a name by its hash code.
      Parameters:
      hashCode - the FNV-1a 64-bit hash code of the name
      Returns:
      the ordinal (1-based) if found, -1 otherwise

    • getOrdinal

      public int getOrdinal(String name)
      Get the ordinal of a name.
      Parameters:
      name - the name to look up
      Returns:
      the ordinal (1-based) if found, -1 otherwise

    • getName

      public String getName(int ordinal)
      Get the name by its ordinal.
      Parameters:
      ordinal - the ordinal (1-based) of the name
      Returns:
      the name at the specified ordinal
      Throws:
      ArrayIndexOutOfBoundsException - if the ordinal is invalid

    • getHashCode

      public long getHashCode(int ordinal)
      Get the hash code of a name by its ordinal.
      Parameters:
      ordinal - the ordinal (1-based) of the name
      Returns:
      the FNV-1a 64-bit hash code of the name at the specified ordinal
      Throws:
      ArrayIndexOutOfBoundsException - if the ordinal is invalid