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Jinterface Java package contains java classes, which help you integrate programs written in Java with Erlang. Erlang is a programming language designed at the Ericsson Computer Science Laboratory.

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/*
 * %CopyrightBegin%
 * 
 * Copyright Ericsson AB 2000-2009. All Rights Reserved.
 * 
 * The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved online at http://www.erlang.org/.
 * 
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 * 
 * %CopyrightEnd%
 */
package com.ericsson.otp.erlang;

import java.io.Serializable;

/**
 * Provides a Java representation of Erlang floats and doubles. Erlang defines
 * only one floating point numeric type, however this class and its subclass
 * {@link OtpErlangFloat} are used to provide representations corresponding to
 * the Java types Double and Float.
 */
public class OtpErlangDouble extends OtpErlangObject implements Serializable,
	Cloneable {
    // don't change this!
    static final long serialVersionUID = 132947104811974021L;

    private final double d;

    /**
     * Create an Erlang float from the given double value.
     */
    public OtpErlangDouble(final double d) {
	this.d = d;
    }

    /**
     * Create an Erlang float from a stream containing a double encoded in
     * Erlang external format.
     * 
     * @param buf
     *                the stream containing the encoded value.
     * 
     * @exception OtpErlangDecodeException
     *                    if the buffer does not contain a valid external
     *                    representation of an Erlang float.
     */
    public OtpErlangDouble(final OtpInputStream buf)
	    throws OtpErlangDecodeException {
	d = buf.read_double();
    }

    /**
     * Get the value, as a double.
     * 
     * @return the value of this object, as a double.
     */
    public double doubleValue() {
	return d;
    }

    /**
     * Get the value, as a float.
     * 
     * @return the value of this object, as a float.
     * 
     * @exception OtpErlangRangeException
     *                    if the value cannot be represented as a float.
     */
    public float floatValue() throws OtpErlangRangeException {
	final float f = (float) d;

	if (f != d) {
	    throw new OtpErlangRangeException("Value too large for float: " + d);
	}

	return f;
    }

    /**
     * Get the string representation of this double.
     * 
     * @return the string representation of this double.
     */
    @Override
    public String toString() {
	return "" + d;
    }

    /**
     * Convert this double to the equivalent Erlang external representation.
     * 
     * @param buf
     *                an output stream to which the encoded value should be
     *                written.
     */
    @Override
    public void encode(final OtpOutputStream buf) {
	buf.write_double(d);
    }

    /**
     * Determine if two floats are equal. Floats are equal if they contain the
     * same value.
     * 
     * @param o
     *                the float to compare to.
     * 
     * @return true if the floats have the same value.
     */
    @Override
    public boolean equals(final Object o) {
	if (!(o instanceof OtpErlangDouble)) {
	    return false;
	}

	final OtpErlangDouble d = (OtpErlangDouble) o;
	return this.d == d.d;
    }
    
    @Override
    protected int doHashCode() {
	Double v = new Double(d);
	return v.hashCode();
    }
}