Jackson is "the Java JSON library" or "the best JSON parser for Java". Or simply as "JSON for Java".

Jackson Core Source Code files are provided in the source packge (jackson-core-2.14.0-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Core Source Code below:

⏎ com/fasterxml/jackson/core/io/doubleparser/DoubleBitsFromCharArray.java

/**
 * References:
 * <dl>
 *     <dt>This class has been derived from "FastDoubleParser".</dt>
 *     <dd>Copyright (c) Werner Randelshofer. Apache 2.0 License.
 *         <a href="https://github.com/wrandelshofer/FastDoubleParser">github.com</a>.</dd>
 * </dl>
 */

package com.fasterxml.jackson.core.io.doubleparser;

/**
 * Parses a {@code double} from a {@code char} array.
 */
final class DoubleBitsFromCharArray extends AbstractFloatingPointBitsFromCharArray {


    /**
     * Creates a new instance.
     */
    public DoubleBitsFromCharArray() {

    }

    @Override
    long nan() {
        return Double.doubleToRawLongBits(Double.NaN);
    }

    @Override
    long negativeInfinity() {
        return Double.doubleToRawLongBits(Double.NEGATIVE_INFINITY);
    }

    @Override
    long positiveInfinity() {
        return Double.doubleToRawLongBits(Double.POSITIVE_INFINITY);
    }

    @Override
    long valueOfFloatLiteral(char[] str, int startIndex, int endIndex, boolean isNegative,
                             long significand, int exponent, boolean isSignificandTruncated,
                             int exponentOfTruncatedSignificand) {
        double d = FastDoubleMath.tryDecFloatToDoubleTruncated(isNegative, significand, exponent, isSignificandTruncated,
                exponentOfTruncatedSignificand);
        return Double.doubleToRawLongBits(Double.isNaN(d) ? Double.parseDouble(new String(str, startIndex, endIndex - startIndex)) : d);
    }

    @Override
    long valueOfHexLiteral(
            char[] str, int startIndex, int endIndex, boolean isNegative, long significand, int exponent,
            boolean isSignificandTruncated, int exponentOfTruncatedSignificand) {
        double d = FastDoubleMath.tryHexFloatToDoubleTruncated(isNegative, significand, exponent, isSignificandTruncated,
                exponentOfTruncatedSignificand);
        return Double.doubleToRawLongBits(Double.isNaN(d) ? Double.parseDouble(new String(str, startIndex, endIndex - startIndex)) : d);
    }

}

⏎ com/fasterxml/jackson/core/io/doubleparser/DoubleBitsFromCharArray.java

Or download all of them as a single archive file:

File name: jackson-core-2.14.0-sources.jar
File size: 497693 bytes
Release date: 2022-11-05
Download 

⇒ Download and Install Jackson Binary Package

⇐ What Is Jackson

⇑ Downloading and Reviewing jackson-*.jar

⇑⇑ Jackson - Java JSON library