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

Jackson Annotations Source Code files are provided in the source packge (jackson-annotations-2.12.4-sources.jar). You can download it at Jackson Maven Website.

You can also browse Jackson Annotations Source Code below:

⏎ com/fasterxml/jackson/databind/util/ArrayBuilders.java

package com.fasterxml.jackson.databind.util;

import java.lang.reflect.Array;
import java.util.*;

/**
 * Helper class that contains set of distinct builders for different
 * arrays of primitive values. It also provides trivially simple
 * reuse scheme, which assumes that caller knows not to use instances
 * concurrently (which works ok with primitive arrays since they can
 * not contain other non-primitive types).
 * Also note that instances are not thread safe; the intent is that
 * a builder is constructed on per-call (deserialization) basis.
 */
public final class ArrayBuilders
{
    private BooleanBuilder _booleanBuilder = null;

    // note: no need for char[] builder, assume they are Strings

    private ByteBuilder _byteBuilder = null;
    private ShortBuilder _shortBuilder = null;
    private IntBuilder _intBuilder = null;
    private LongBuilder _longBuilder = null;
    
    private FloatBuilder _floatBuilder = null;
    private DoubleBuilder _doubleBuilder = null;

    public ArrayBuilders() { }

    public BooleanBuilder getBooleanBuilder()
    {
        if (_booleanBuilder == null) {
            _booleanBuilder = new BooleanBuilder();
        }
        return _booleanBuilder;
    }

    public ByteBuilder getByteBuilder()
    {
        if (_byteBuilder == null) {
            _byteBuilder = new ByteBuilder();
        }
        return _byteBuilder;
    }
    public ShortBuilder getShortBuilder()
    {
        if (_shortBuilder == null) {
            _shortBuilder = new ShortBuilder();
        }
        return _shortBuilder;
    }
    public IntBuilder getIntBuilder()
    {
        if (_intBuilder == null) {
            _intBuilder = new IntBuilder();
        }
        return _intBuilder;
    }
    public LongBuilder getLongBuilder()
    {
        if (_longBuilder == null) {
            _longBuilder = new LongBuilder();
        }
        return _longBuilder;
    }

    public FloatBuilder getFloatBuilder()
    {
        if (_floatBuilder == null) {
            _floatBuilder = new FloatBuilder();
        }
        return _floatBuilder;
    }
    public DoubleBuilder getDoubleBuilder()
    {
        if (_doubleBuilder == null) {
            _doubleBuilder = new DoubleBuilder();
        }
        return _doubleBuilder;
    }

    /*
    /**********************************************************
    /* Impl classes
    /**********************************************************
     */

    public final static class BooleanBuilder
        extends PrimitiveArrayBuilder<boolean[]>
    {
        public BooleanBuilder() { }
        @Override
        public final boolean[] _constructArray(int len) { return new boolean[len]; }
    }

    public final static class ByteBuilder
        extends PrimitiveArrayBuilder<byte[]>
    {
        public ByteBuilder() { }
        @Override
        public final byte[] _constructArray(int len) { return new byte[len]; }
    }
    public final static class ShortBuilder
        extends PrimitiveArrayBuilder<short[]>
    {
        public ShortBuilder() { }
        @Override
        public final short[] _constructArray(int len) { return new short[len]; }
    }
    public final static class IntBuilder
        extends PrimitiveArrayBuilder<int[]>
    {
        public IntBuilder() { }
        @Override
        public final int[] _constructArray(int len) { return new int[len]; }
    }
    public final static class LongBuilder
        extends PrimitiveArrayBuilder<long[]>
    {
        public LongBuilder() { }
        @Override
        public final long[] _constructArray(int len) { return new long[len]; }
    }

    public final static class FloatBuilder
        extends PrimitiveArrayBuilder<float[]>
    {
        public FloatBuilder() { }
        @Override
        public final float[] _constructArray(int len) { return new float[len]; }
    }
    public final static class DoubleBuilder
        extends PrimitiveArrayBuilder<double[]>
    {
        public DoubleBuilder() { }
        @Override
        public final double[] _constructArray(int len) { return new double[len]; }
    }
    
    /*
    /**********************************************************
    /* Static helper methods
    /**********************************************************
     */

    /**
     * Helper method used for constructing simple value comparator used for
     * comparing arrays for content equality.
     *<p>
     * Note: current implementation is not optimized for speed; if performance
     * ever becomes an issue, it is possible to construct much more efficient
     * typed instances (one for Object[] and sub-types; one per primitive type).
     * 
     * @since 2.2 Moved from earlier <code>Comparators</code> class
     */
    public static Object getArrayComparator(final Object defaultValue)
    {
        final int length = Array.getLength(defaultValue);
        final Class<?> defaultValueType = defaultValue.getClass();
        return new Object() {
            @Override
            public boolean equals(Object other) {
                if (other == this) return true;
                if (!ClassUtil.hasClass(other, defaultValueType)) {
                    return false;
                }
                if (Array.getLength(other) != length) return false;
                // so far so good: compare actual equality; but only shallow one
                for (int i = 0; i < length; ++i) {
                    Object value1 = Array.get(defaultValue, i);
                    Object value2 = Array.get(other, i);
                    if (value1 == value2) continue;
                    if (value1 != null) {
                        if (!value1.equals(value2)) {
                            return false;
                        }
                    }
                }
                return true;
            }
        };
    }

    public static <T> HashSet<T> arrayToSet(T[] elements)
    {
        if (elements != null) {
            int len = elements.length;
            HashSet<T> result = new HashSet<T>(len);
            for (int i = 0; i < len; ++i) {
                result.add(elements[i]);
            }
            return result;
        }
        return new HashSet<T>();
    }

    /**
     * Helper method for constructing a new array that contains specified
     * element followed by contents of the given array but never contains
     * duplicates.
     * If element already existed, one of two things happens: if the element
     * was already the first one in array, array is returned as is; but
     * if not, a new copy is created in which element has moved as the head.
     */
    @SuppressWarnings("unchecked")
    public static <T> T[] insertInListNoDup(T[] array, T element)
    {
        final int len = array.length;
        
        // First: see if the element already exists
        for (int ix = 0; ix < len; ++ix) {
            if (array[ix] == element) {
                // if at head already, return as is
                if (ix == 0) {
                    return array;
                }
                // otherwise move things around
                T[] result = (T[]) Array.newInstance(array.getClass().getComponentType(), len);
                System.arraycopy(array, 0, result, 1, ix);
                result[0] = element;
                ++ix;
                int left = len - ix;
                if (left > 0) {
                	System.arraycopy(array, ix, result, ix, left);
                }
                return result;
            }
        }

        // but if not, allocate new array, move
        T[] result = (T[]) Array.newInstance(array.getClass().getComponentType(), len+1);
        if (len > 0) {
            System.arraycopy(array, 0, result, 1, len);
        }
        result[0] = element;
        return result;
    }
}

⏎ com/fasterxml/jackson/databind/util/ArrayBuilders.java

 

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