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Java example source code file (DfpDec.java)

This example Java source code file (DfpDec.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

dfp, dfpdec, dfpfield, infinite, min_exp, override, qnan, radix, round_ceil, round_half_down, round_half_even, round_half_up, round_up, string

The DfpDec.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.math3.dfp;

/** Subclass of {@link Dfp} which hides the radix-10000 artifacts of the superclass.
 * This should give outward appearances of being a decimal number with DIGITS*4-3
 * decimal digits. This class can be subclassed to appear to be an arbitrary number
 * of decimal digits less than DIGITS*4-3.
 * @since 2.2
 */
public class DfpDec extends Dfp {

    /** Makes an instance with a value of zero.
     * @param factory factory linked to this instance
     */
    protected DfpDec(final DfpField factory) {
        super(factory);
    }

    /** Create an instance from a byte value.
     * @param factory factory linked to this instance
     * @param x value to convert to an instance
     */
    protected DfpDec(final DfpField factory, byte x) {
        super(factory, x);
    }

    /** Create an instance from an int value.
     * @param factory factory linked to this instance
     * @param x value to convert to an instance
     */
    protected DfpDec(final DfpField factory, int x) {
        super(factory, x);
    }

    /** Create an instance from a long value.
     * @param factory factory linked to this instance
     * @param x value to convert to an instance
     */
    protected DfpDec(final DfpField factory, long x) {
        super(factory, x);
    }

    /** Create an instance from a double value.
     * @param factory factory linked to this instance
     * @param x value to convert to an instance
     */
    protected DfpDec(final DfpField factory, double x) {
        super(factory, x);
        round(0);
    }

    /** Copy constructor.
     * @param d instance to copy
     */
    public DfpDec(final Dfp d) {
        super(d);
        round(0);
    }

    /** Create an instance from a String representation.
     * @param factory factory linked to this instance
     * @param s string representation of the instance
     */
    protected DfpDec(final DfpField factory, final String s) {
        super(factory, s);
        round(0);
    }

    /** Creates an instance with a non-finite value.
     * @param factory factory linked to this instance
     * @param sign sign of the Dfp to create
     * @param nans code of the value, must be one of {@link #INFINITE},
     * {@link #SNAN},  {@link #QNAN}
     */
    protected DfpDec(final DfpField factory, final byte sign, final byte nans) {
        super(factory, sign, nans);
    }

    /** {@inheritDoc} */
    @Override
    public Dfp newInstance() {
        return new DfpDec(getField());
    }

    /** {@inheritDoc} */
    @Override
    public Dfp newInstance(final byte x) {
        return new DfpDec(getField(), x);
    }

    /** {@inheritDoc} */
    @Override
    public Dfp newInstance(final int x) {
        return new DfpDec(getField(), x);
    }

    /** {@inheritDoc} */
    @Override
    public Dfp newInstance(final long x) {
        return new DfpDec(getField(), x);
    }

    /** {@inheritDoc} */
    @Override
    public Dfp newInstance(final double x) {
        return new DfpDec(getField(), x);
    }

    /** {@inheritDoc} */
    @Override
    public Dfp newInstance(final Dfp d) {

        // make sure we don't mix number with different precision
        if (getField().getRadixDigits() != d.getField().getRadixDigits()) {
            getField().setIEEEFlagsBits(DfpField.FLAG_INVALID);
            final Dfp result = newInstance(getZero());
            result.nans = QNAN;
            return dotrap(DfpField.FLAG_INVALID, "newInstance", d, result);
        }

        return new DfpDec(d);

    }

    /** {@inheritDoc} */
    @Override
    public Dfp newInstance(final String s) {
        return new DfpDec(getField(), s);
    }

    /** {@inheritDoc} */
    @Override
    public Dfp newInstance(final byte sign, final byte nans) {
        return new DfpDec(getField(), sign, nans);
    }

    /** Get the number of decimal digits this class is going to represent.
     * Default implementation returns {@link #getRadixDigits()}*4-3. Subclasses can
     * override this to return something less.
     * @return number of decimal digits this class is going to represent
     */
    protected int getDecimalDigits() {
        return getRadixDigits() * 4 - 3;
    }

    /** {@inheritDoc} */
    @Override
    protected int round(int in) {

        int msb = mant[mant.length-1];
        if (msb == 0) {
            // special case -- this == zero
            return 0;
        }

        int cmaxdigits = mant.length * 4;
        int lsbthreshold = 1000;
        while (lsbthreshold > msb) {
            lsbthreshold /= 10;
            cmaxdigits --;
        }


        final int digits = getDecimalDigits();
        final int lsbshift = cmaxdigits - digits;
        final int lsd = lsbshift / 4;

        lsbthreshold = 1;
        for (int i = 0; i < lsbshift % 4; i++) {
            lsbthreshold *= 10;
        }

        final int lsb = mant[lsd];

        if (lsbthreshold <= 1 && digits == 4 * mant.length - 3) {
            return super.round(in);
        }

        int discarded = in;  // not looking at this after this point
        final int n;
        if (lsbthreshold == 1) {
            // look to the next digit for rounding
            n = (mant[lsd-1] / 1000) % 10;
            mant[lsd-1] %= 1000;
            discarded |= mant[lsd-1];
        } else {
            n = (lsb * 10 / lsbthreshold) % 10;
            discarded |= lsb % (lsbthreshold/10);
        }

        for (int i = 0; i < lsd; i++) {
            discarded |= mant[i];    // need to know if there are any discarded bits
            mant[i] = 0;
        }

        mant[lsd] = lsb / lsbthreshold * lsbthreshold;

        final boolean inc;
        switch (getField().getRoundingMode()) {
            case ROUND_DOWN:
                inc = false;
                break;

            case ROUND_UP:
                inc = (n != 0) || (discarded != 0); // round up if n!=0
                break;

            case ROUND_HALF_UP:
                inc = n >= 5;  // round half up
                break;

            case ROUND_HALF_DOWN:
                inc = n > 5;  // round half down
                break;

            case ROUND_HALF_EVEN:
                inc = (n > 5) ||
                      (n == 5 && discarded != 0) ||
                      (n == 5 && discarded == 0 && ((lsb / lsbthreshold) & 1) == 1);  // round half-even
                break;

            case ROUND_HALF_ODD:
                inc = (n > 5) ||
                      (n == 5 && discarded != 0) ||
                      (n == 5 && discarded == 0 && ((lsb / lsbthreshold) & 1) == 0);  // round half-odd
                break;

            case ROUND_CEIL:
                inc = (sign == 1) && (n != 0 || discarded != 0);  // round ceil
                break;

            case ROUND_FLOOR:
            default:
                inc = (sign == -1) && (n != 0 || discarded != 0);  // round floor
                break;
        }

        if (inc) {
            // increment if necessary
            int rh = lsbthreshold;
            for (int i = lsd; i < mant.length; i++) {
                final int r = mant[i] + rh;
                rh = r / RADIX;
                mant[i] = r % RADIX;
            }

            if (rh != 0) {
                shiftRight();
                mant[mant.length-1]=rh;
            }
        }

        // Check for exceptional cases and raise signals if necessary
        if (exp < MIN_EXP) {
            // Gradual Underflow
            getField().setIEEEFlagsBits(DfpField.FLAG_UNDERFLOW);
            return DfpField.FLAG_UNDERFLOW;
        }

        if (exp > MAX_EXP) {
            // Overflow
            getField().setIEEEFlagsBits(DfpField.FLAG_OVERFLOW);
            return DfpField.FLAG_OVERFLOW;
        }

        if (n != 0 || discarded != 0) {
            // Inexact
            getField().setIEEEFlagsBits(DfpField.FLAG_INEXACT);
            return DfpField.FLAG_INEXACT;
        }
        return 0;
    }

    /** {@inheritDoc} */
    @Override
    public Dfp nextAfter(Dfp x) {

        final String trapName = "nextAfter";

        // make sure we don't mix number with different precision
        if (getField().getRadixDigits() != x.getField().getRadixDigits()) {
            getField().setIEEEFlagsBits(DfpField.FLAG_INVALID);
            final Dfp result = newInstance(getZero());
            result.nans = QNAN;
            return dotrap(DfpField.FLAG_INVALID, trapName, x, result);
        }

        boolean up = false;
        Dfp result;
        Dfp inc;

        // if this is greater than x
        if (this.lessThan(x)) {
            up = true;
        }

        if (equals(x)) {
            return newInstance(x);
        }

        if (lessThan(getZero())) {
            up = !up;
        }

        if (up) {
            inc = power10(intLog10() - getDecimalDigits() + 1);
            inc = copysign(inc, this);

            if (this.equals(getZero())) {
                inc = power10K(MIN_EXP-mant.length-1);
            }

            if (inc.equals(getZero())) {
                result = copysign(newInstance(getZero()), this);
            } else {
                result = add(inc);
            }
        } else {
            inc = power10(intLog10());
            inc = copysign(inc, this);

            if (this.equals(inc)) {
                inc = inc.divide(power10(getDecimalDigits()));
            } else {
                inc = inc.divide(power10(getDecimalDigits() - 1));
            }

            if (this.equals(getZero())) {
                inc = power10K(MIN_EXP-mant.length-1);
            }

            if (inc.equals(getZero())) {
                result = copysign(newInstance(getZero()), this);
            } else {
                result = subtract(inc);
            }
        }

        if (result.classify() == INFINITE && this.classify() != INFINITE) {
            getField().setIEEEFlagsBits(DfpField.FLAG_INEXACT);
            result = dotrap(DfpField.FLAG_INEXACT, trapName, x, result);
        }

        if (result.equals(getZero()) && this.equals(getZero()) == false) {
            getField().setIEEEFlagsBits(DfpField.FLAG_INEXACT);
            result = dotrap(DfpField.FLAG_INEXACT, trapName, x, result);
        }

        return result;
    }

}

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