javolution.lang

Interface ValueType<T>

Type Parameters:

T - The type of the immutable constant value.

All Superinterfaces:

Immutable<T>

All Known Implementing Classes:

Index, Text

public interface ValueType<T>
extends Immutable<T>

An immutable object which can be manipulated by value; a JVM implementation may allocate instances of this class on the stack.

ValueType extends Immutable with the additional constraint that its value is itself (the value method returns this).

 public final class Complex implements ValueType<Complex> { // Complex is immutable.
     public class Variable implements Immutable<Complex> { // Variable has immutable value.
         private Variable() {} // Do not provide access outside.
         public Variable add(Complex that) {
              real += that.real;
              imaginary += that.imaginary;
              return this;
         }
         @Override
         public Complex value() { return new Complex(real, imaginary); }
     }
     private double real, imaginary;
     public Complex(double real, double imaginary) {
         this.real = real;
         this.imaginary = imaginary;
     }
     public Complex plus(Complex that) { 
         return new Complex(this.real + that.real, this.imaginary + this.imaginary);
     }
     @Override
     public Complex value() { return this; } // As per ValueType contract.
     public Variable newVariable() { return new Complex(real, imaginary).new Variable(); }
 }
 // Calculates the sum of an array of complex values. 
 Complex[] values = ...;
 
 // Standard calculations (stresses GC due to the high number of objects allocated).
 Complex sum = Complex.ZERO;
 for (Complex c : values) sum = sum.plus(c);
 
 // Using variables, 2-3x faster and almost no garbage generated !
 Complex.Variable sum = Complex.ZERO.newVariable();
 for (Complex c : values) sum.add(c); 
 

Note: "Stack" allocation is not the only optimization that a VM can do on ValueType. The VM might decide not to perform any allocation at all and store values directly in registers.

Version:

6.0, July 21, 2013

Author:

Jean-Marie Dautelle

Method Summary

Methods

Modifier and Type	Method and Description
T	value() Returns this.

Method Detail

value

T value()

Returns this.

Specified by:

value in interface Immutable<T>