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/JsonTokenId.java

package com.fasterxml.jackson.core;

/**
 * Interface defined to contain ids accessible with {@link JsonToken#id()}.
 * Needed because it is impossible to define these constants in
 * {@link JsonToken} itself, as static constants (oddity of how Enums
 * are implemented by JVM).
 * 
 * @since 2.3
 */
public interface JsonTokenId
{
    /**
     * Id used to represent {@link JsonToken#NOT_AVAILABLE}, used in
     * cases where a token may become available when more input
     * is available: this occurs in non-blocking use cases.
     */
    public final static int ID_NOT_AVAILABLE = -1;

    /**
     * Id used to represent the case where no {@link JsonToken}
     * is available: either because {@link JsonParser} has not been
     * advanced to first token, or because no more tokens will be
     * available (end-of-input or explicit closing of parser}.
     */
    public final static int ID_NO_TOKEN = 0;

    /**
     * Id used to represent {@link JsonToken#START_OBJECT}
     */
    public final static int ID_START_OBJECT = 1;

    /**
     * Id used to represent {@link JsonToken#END_OBJECT}
     */
    public final static int ID_END_OBJECT = 2;

    /**
     * Id used to represent {@link JsonToken#START_ARRAY}
     */
    public final static int ID_START_ARRAY = 3;

    /**
     * Id used to represent {@link JsonToken#END_ARRAY}
     */
    public final static int ID_END_ARRAY = 4;

    /**
     * Id used to represent {@link JsonToken#FIELD_NAME}
     */
    public final static int ID_FIELD_NAME = 5;

    /**
     * Id used to represent {@link JsonToken#VALUE_STRING}
     */
    public final static int ID_STRING = 6;

    /**
     * Id used to represent {@link JsonToken#VALUE_NUMBER_INT}
     */
    public final static int ID_NUMBER_INT = 7;

    /**
     * Id used to represent {@link JsonToken#VALUE_NUMBER_FLOAT}
     */
    public final static int ID_NUMBER_FLOAT = 8;

    /**
     * Id used to represent {@link JsonToken#VALUE_TRUE}
     */
    public final static int ID_TRUE = 9;

    /**
     * Id used to represent {@link JsonToken#VALUE_FALSE}
     */
    public final static int ID_FALSE = 10;
    /**
     * Id used to represent {@link JsonToken#VALUE_NULL}
     */

    public final static int ID_NULL = 11;

    /**
     * Id used to represent {@link JsonToken#VALUE_EMBEDDED_OBJECT}
     */
    public final static int ID_EMBEDDED_OBJECT = 12;
}

⏎ com/fasterxml/jackson/core/JsonTokenId.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