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  package com.fasterxml.jackson.databind;
  
  import java.util.*;
  
Base class for all JSON nodes, which form the basis of JSON Tree Model that Jackson implements. One way to think of these nodes is to consider them similar to DOM nodes in XML DOM trees.

As a general design rule, most accessors ("getters") are included in this base class, to allow for traversing structure without type casts. Most mutators, however, need to be accessed through specific sub-classes (such as ObjectNode and ArrayNode). This seems sensible because proper type information is generally available when building or modifying trees, but less often when reading a tree (newly built from parsed JSON content).

Actual concrete sub-classes can be found from package com.fasterxml.jackson.databind.node.

 
 public abstract class JsonNode
     implements TreeNodeIterable<JsonNode>
 {
     /*
     /**********************************************************
     /* Construction, related
     /**********************************************************
      */
     
     protected JsonNode() { }

    
Method that can be called to get a node that is guaranteed not to allow changing of this node through mutators on this node or any of its children. This means it can either make a copy of this node (and all mutable children and grand children nodes), or node itself if it is immutable.

Note: return type is guaranteed to have same type as the node method is called on; which is why method is declared with local generic type.

Returns:
Node that is either a copy of this node (and all non-leaf children); or, for immutable leaf nodes, node itself.
Since:
2.0
 
     public abstract <T extends JsonNode> T deepCopy();
 
     /*
     /**********************************************************
     /* TreeNode implementation
     /**********************************************************
      */
 
 //    public abstract JsonToken asToken();
 
 //    public abstract JsonParser.NumberType numberType();
 
 //    public abstract JsonParser traverse();
 
     @Override
     public int size() { return 0; }
 
     @Override
     public final boolean isValueNode()
     {
         switch (getNodeType()) {
             case case case :
                 return false;
             default:
                 return true;
         }
     }
 
     @Override
     public final boolean isContainerNode() {
         final JsonNodeType type = getNodeType();
         return type == . || type == .;
     }
 
     @Override
     public final boolean isMissingNode() {
         return getNodeType() == .;
     }
 
    @Override
    public final boolean isArray() {
        return getNodeType() == .;
    }
    @Override
    public final boolean isObject() {
        return getNodeType() == .;
    }

    
Method for accessing value of the specified element of an array node. For other nodes, null is always returned.

For array nodes, index specifies exact location within array and allows for efficient iteration over child elements (underlying storage is guaranteed to be efficiently indexable, i.e. has random-access to elements). If index is less than 0, or equal-or-greater than node.size(), null is returned; no exception is thrown for any index.

NOTE: if the element value has been explicitly set as null (which is different from removal!), a com.fasterxml.jackson.databind.node.NullNode will be returned, not null.

Returns:
Node that represent value of the specified element, if this node is an array and has specified element. Null otherwise.
    @Override
    public abstract JsonNode get(int index);

    
Method for accessing value of the specified field of an object node. If this node is not an object (or it does not have a value for specified field name), or if there is no field with such name, null is returned.

NOTE: if the property value has been explicitly set as null (which is different from removal!), a com.fasterxml.jackson.databind.node.NullNode will be returned, not null.

Returns:
Node that represent value of the specified field, if this node is an object and has value for the specified field. Null otherwise.
    @Override
    public JsonNode get(String fieldName) { return null; }
    
This method is similar to get(java.lang.String), except that instead of returning null if no such value exists (due to this node not being an object, or object not having value for the specified field), a "missing node" (node that returns true for isMissingNode()) will be returned. This allows for convenient and safe chained access via path calls.
    @Override
    public abstract JsonNode path(String fieldName);

    
This method is similar to get(int), except that instead of returning null if no such element exists (due to index being out of range, or this node not being an array), a "missing node" (node that returns true for isMissingNode()) will be returned. This allows for convenient and safe chained access via path calls.
    @Override
    public abstract JsonNode path(int index);
    @Override
    public Iterator<StringfieldNames() {
        return EmptyIterator.instance();
    }
    @Override
    public final JsonNode at(JsonPointer ptr)
    {
        // Basically: value nodes only match if we have "empty" path left
        if (ptr.matches()) {
            return this;
        }
        JsonNode n = _at(ptr);
        if (n == null) {
            return MissingNode.getInstance();
        }
        return n.at(ptr.tail());
    }
    @Override
    public final JsonNode at(String jsonPtrExpr) {
        return at(JsonPointer.compile(jsonPtrExpr));
    }
    protected abstract JsonNode _at(JsonPointer ptr);
    
    /*
    /**********************************************************
    /* Public API, type introspection
    /**********************************************************
     */
    // // First high-level division between values, containers and "missing"

    
Return the type of this node

Returns:
the node type as a com.fasterxml.jackson.databind.node.JsonNodeType enum value
Since:
2.2
    public abstract JsonNodeType getNodeType();

    
Method that can be used to check if the node is a wrapper for a POJO ("Plain Old Java Object" aka "bean". Returns true only for instances of POJONode.

Returns:
True if this node wraps a POJO
    public final boolean isPojo() {
        return getNodeType() == .;
    }

    

Returns:
True if this node represents a numeric JSON value
    public final boolean isNumber() {
        return getNodeType() == .;
    }

    

Returns:
True if this node represents an integral (integer) numeric JSON value
    public boolean isIntegralNumber() { return false; }

    

Returns:
True if this node represents a non-integral numeric JSON value
    public boolean isFloatingPointNumber() { return false; }

    
Method that can be used to check whether contained value is a number represented as Java short. Note, however, that even if this method returns false, it is possible that conversion would be possible from other numeric types -- to check if this is possible, use canConvertToInt() instead.

Returns:
True if the value contained by this node is stored as Java short
    public boolean isShort() { return false; }

    
Method that can be used to check whether contained value is a number represented as Java int. Note, however, that even if this method returns false, it is possible that conversion would be possible from other numeric types -- to check if this is possible, use canConvertToInt() instead.

Returns:
True if the value contained by this node is stored as Java int
    public boolean isInt() { return false; }

    
Method that can be used to check whether contained value is a number represented as Java long. Note, however, that even if this method returns false, it is possible that conversion would be possible from other numeric types -- to check if this is possible, use canConvertToInt() instead.

Returns:
True if the value contained by this node is stored as Java long
    public boolean isLong() { return false; }

    

Since:
2.2
    public boolean isFloat() { return false; }
    public boolean isDouble() { return false; }
    public boolean isBigDecimal() { return false; }
    public boolean isBigInteger() { return false; }

    
Method that checks whether this node represents basic JSON String value.
    public final boolean isTextual() {
        return getNodeType() == .;
    }

    
Method that can be used to check if this node was created from JSON boolean value (literals "true" and "false").
    public final boolean isBoolean() {
        return getNodeType() == .;
    }

    
Method that can be used to check if this node was created from JSON literal null value.
    public final boolean isNull() {
        return getNodeType() == .;
    }

    
Method that can be used to check if this node represents binary data (Base64 encoded). Although this will be externally written as JSON String value, isTextual() will return false if this method returns true.

Returns:
True if this node represents base64 encoded binary data
    public final boolean isBinary() {
        return getNodeType() == .;
    }

    
Method that can be used to check whether this node is a numeric node (isNumber() would return true) AND its value fits within Java's 32-bit signed integer type, int. Note that floating-point numbers are convertible if the integral part fits without overflow (as per standard Java coercion rules)

Since:
2.0
    public boolean canConvertToInt() { return false; }

    
Method that can be used to check whether this node is a numeric node (isNumber() would return true) AND its value fits within Java's 64-bit signed integer type, long. Note that floating-point numbers are convertible if the integral part fits without overflow (as per standard Java coercion rules)

Since:
2.0
    public boolean canConvertToLong() { return false; }
    
    /*
    /**********************************************************
    /* Public API, straight value access
    /**********************************************************
     */

    
Method to use for accessing String values. Does NOT do any conversions for non-String value nodes; for non-String values (ones for which isTextual() returns false) null will be returned. For String values, null is never returned (but empty Strings may be)

Returns:
Textual value this node contains, iff it is a textual JSON node (comes from JSON String value entry)
    public String textValue() { return null; }

    
Method to use for accessing binary content of binary nodes (nodes for which isBinary() returns true); or for Text Nodes (ones for which textValue() returns non-null value), to read decoded base64 data. For other types of nodes, returns null.

Returns:
Binary data this node contains, iff it is a binary node; null otherwise
    public byte[] binaryValue() throws IOException {
        return null;
    }

    
Method to use for accessing JSON boolean values (value literals 'true' and 'false'). For other types, always returns false.

Returns:
Textual value this node contains, iff it is a textual json node (comes from JSON String value entry)
    public boolean booleanValue() { return false; }

    
Returns numeric value for this node, if and only if this node is numeric (isNumber() returns true); otherwise returns null

Returns:
Number value this node contains, if any (null for non-number nodes).
    public Number numberValue() { return null; }

    
Returns 16-bit short value for this node, if and only if this node is numeric (isNumber() returns true). For other types returns 0. For floating-point numbers, value is truncated using default Java coercion, similar to how cast from double to short operates.

Returns:
Short value this node contains, if any; 0 for non-number nodes.
    public short shortValue() { return 0; }

    
Returns integer value for this node, if and only if this node is numeric (isNumber() returns true). For other types returns 0. For floating-point numbers, value is truncated using default Java coercion, similar to how cast from double to int operates.

Returns:
Integer value this node contains, if any; 0 for non-number nodes.
    public int intValue() { return 0; }

    
Returns 64-bit long value for this node, if and only if this node is numeric (isNumber() returns true). For other types returns 0. For floating-point numbers, value is truncated using default Java coercion, similar to how cast from double to long operates.

Returns:
Long value this node contains, if any; 0 for non-number nodes.
    public long longValue() { return 0L; }
    
    
Returns 32-bit floating value for this node, if and only if this node is numeric (isNumber() returns true). For other types returns 0.0. For integer values, conversion is done using coercion; this means that an overflow is possible for `long` values

Returns:
32-bit float value this node contains, if any; 0.0 for non-number nodes.
Since:
2.2
    public float floatValue() { return 0.0f; }

    
Returns 64-bit floating point (double) value for this node, if and only if this node is numeric (isNumber() returns true). For other types returns 0.0. For integer values, conversion is done using coercion; this may result in overflows with java.math.BigInteger values.

Returns:
64-bit double value this node contains, if any; 0.0 for non-number nodes.
Since:
2.2
    public double doubleValue() { return 0.0; }
    public BigDecimal decimalValue() { return .; }
    public BigInteger bigIntegerValue() { return .; }
    
    /*
    /**********************************************************
    /* Public API, value access with conversion(s)/coercion(s)
    /**********************************************************
     */

    
Method that will return a valid String representation of the container value, if the node is a value node (method isValueNode() returns true), otherwise empty String.
    public abstract String asText();

    
Method that will try to convert value of this node to a Java int. Numbers are coerced using default Java rules; booleans convert to 0 (false) and 1 (true), and Strings are parsed using default Java language integer parsing rules.

If representation can not be converted to an int (including structured types like Objects and Arrays), default value of 0 will be returned; no exceptions are thrown.

    public int asInt() {
        return asInt(0);
    }
    
    
Method that will try to convert value of this node to a Java int. Numbers are coerced using default Java rules; booleans convert to 0 (false) and 1 (true), and Strings are parsed using default Java language integer parsing rules.

If representation can not be converted to an int (including structured types like Objects and Arrays), specified defaultValue will be returned; no exceptions are thrown.

    public int asInt(int defaultValue) {
        return defaultValue;
    }

    
Method that will try to convert value of this node to a Java long. Numbers are coerced using default Java rules; booleans convert to 0 (false) and 1 (true), and Strings are parsed using default Java language integer parsing rules.

If representation can not be converted to an long (including structured types like Objects and Arrays), default value of 0 will be returned; no exceptions are thrown.

    public long asLong() {
        return asLong(0L);
    }
    
    
Method that will try to convert value of this node to a Java long. Numbers are coerced using default Java rules; booleans convert to 0 (false) and 1 (true), and Strings are parsed using default Java language integer parsing rules.

If representation can not be converted to an long (including structured types like Objects and Arrays), specified defaultValue will be returned; no exceptions are thrown.

    public long asLong(long defaultValue) {
        return defaultValue;
    }
    
    
Method that will try to convert value of this node to a Java double. Numbers are coerced using default Java rules; booleans convert to 0.0 (false) and 1.0 (true), and Strings are parsed using default Java language integer parsing rules.

If representation can not be converted to an int (including structured types like Objects and Arrays), default value of 0.0 will be returned; no exceptions are thrown.

    public double asDouble() {
        return asDouble(0.0);
    }
    
    
Method that will try to convert value of this node to a Java double. Numbers are coerced using default Java rules; booleans convert to 0.0 (false) and 1.0 (true), and Strings are parsed using default Java language integer parsing rules.

If representation can not be converted to an int (including structured types like Objects and Arrays), specified defaultValue will be returned; no exceptions are thrown.

    public double asDouble(double defaultValue) {
        return defaultValue;
    }

    
Method that will try to convert value of this node to a Java boolean. JSON booleans map naturally; integer numbers other than 0 map to true, and 0 maps to false and Strings 'true' and 'false' map to corresponding values.

If representation can not be converted to a boolean value (including structured types like Objects and Arrays), default value of false will be returned; no exceptions are thrown.

    public boolean asBoolean() {
        return asBoolean(false);
    }
    
    
Method that will try to convert value of this node to a Java boolean. JSON booleans map naturally; integer numbers other than 0 map to true, and 0 maps to false and Strings 'true' and 'false' map to corresponding values.

If representation can not be converted to a boolean value (including structured types like Objects and Arrays), specified defaultValue will be returned; no exceptions are thrown.

    public boolean asBoolean(boolean defaultValue) {
        return defaultValue;
    }
    
    /*
    /**********************************************************
    /* Public API, value find / existence check methods
    /**********************************************************
     */
    
    
Method that allows checking whether this node is JSON Object node and contains value for specified property. If this is the case (including properties with explicit null values), returns true; otherwise returns false.

This method is equivalent to:

   node.get(fieldName) != null
(since return value of get() is node, not value node contains)

NOTE: when explicit null values are added, this method will return true for such properties.

Parameters:
fieldName Name of element to check
Returns:
True if this node is a JSON Object node, and has a property entry with specified name (with any value, including null value)
    public boolean has(String fieldName) {
        return get(fieldName) != null;
    }

    
Method that allows checking whether this node is JSON Array node and contains a value for specified index If this is the case (including case of specified indexing having null as value), returns true; otherwise returns false.

Note: array element indexes are 0-based.

This method is equivalent to:

   node.get(index) != null

NOTE: this method will return true for explicitly added null values.

Parameters:
index Index to check
Returns:
True if this node is a JSON Object node, and has a property entry with specified name (with any value, including null value)
    public boolean has(int index) {
        return get(index) != null;
    }

    
Method that is similar to has(java.lang.String), but that will return false for explicitly added nulls.

This method is functionally equivalent to:

   node.get(fieldName) != null && !node.get(fieldName).isNull()

Since:
2.1
    public boolean hasNonNull(String fieldName) {
        JsonNode n = get(fieldName);
        return (n != null) && !n.isNull();
    }

    
Method that is similar to has(int), but that will return false for explicitly added nulls.

This method is equivalent to:

   node.get(index) != null && !node.get(index).isNull()

Since:
2.1
    public boolean hasNonNull(int index) {
        JsonNode n = get(index);
        return (n != null) && !n.isNull();
    }
    /*
    /**********************************************************
    /* Public API, container access
    /**********************************************************
     */

    
Same as calling elements(); implemented so that convenience "for-each" loop can be used for looping over elements of JSON Array constructs.
    @Override
    public final Iterator<JsonNodeiterator() { return elements(); }

    
Method for accessing all value nodes of this Node, iff this node is a JSON Array or Object node. In case of Object node, field names (keys) are not included, only values. For other types of nodes, returns empty iterator.
    public Iterator<JsonNodeelements() {
        return EmptyIterator.instance();
    }

    

Returns:
Iterator that can be used to traverse all key/value pairs for object nodes; empty iterator (no contents) for other types
    public Iterator<Map.Entry<StringJsonNode>> fields() {
        return EmptyIterator.instance();
    }
    
    /*
    /**********************************************************
    /* Public API, find methods
    /**********************************************************
     */
    
    
Method for finding a JSON Object field with specified name in this node or its child nodes, and returning value it has. If no matching field is found in this node or its descendants, returns null.

Parameters:
fieldName Name of field to look for
Returns:
Value of first matching node found, if any; null if none
    public abstract JsonNode findValue(String fieldName);

    
Method for finding JSON Object fields with specified name, and returning found ones as a List. Note that sub-tree search ends if a field is found, so possible children of result nodes are not included. If no matching fields are found in this node or its descendants, returns an empty List.

Parameters:
fieldName Name of field to look for
    public final List<JsonNodefindValues(String fieldName)
    {
        List<JsonNoderesult = findValues(fieldNamenull);
        if (result == null) {
            return Collections.emptyList();
        }
        return result;
    }

    
Similar to findValues(java.lang.String), but will additionally convert values into Strings, calling asText().
    public final List<StringfindValuesAsText(String fieldName)
    {
        List<Stringresult = findValuesAsText(fieldNamenull);
        if (result == null) {
            return Collections.emptyList();
        }
        return result;
    }
    
    
Method similar to findValue(java.lang.String), but that will return a "missing node" instead of null if no field is found. Missing node is a specific kind of node for which isMissingNode() returns true; and all value access methods return empty or missing value.

Parameters:
fieldName Name of field to look for
Returns:
Value of first matching node found; or if not found, a "missing node" (non-null instance that has no value)
    public abstract JsonNode findPath(String fieldName);
    
    
Method for finding a JSON Object that contains specified field, within this node or its descendants. If no matching field is found in this node or its descendants, returns null.

Parameters:
fieldName Name of field to look for
Returns:
Value of first matching node found, if any; null if none
    public abstract JsonNode findParent(String fieldName);

    
Method for finding a JSON Object that contains specified field, within this node or its descendants. If no matching field is found in this node or its descendants, returns null.

Parameters:
fieldName Name of field to look for
Returns:
Value of first matching node found, if any; null if none
    public final List<JsonNodefindParents(String fieldName)
    {
        List<JsonNoderesult = findParents(fieldNamenull);
        if (result == null) {
            return Collections.emptyList();
        }
        return result;
    }
    public abstract List<JsonNodefindValues(String fieldNameList<JsonNodefoundSoFar);
    public abstract List<StringfindValuesAsText(String fieldNameList<StringfoundSoFar);
    public abstract List<JsonNodefindParents(String fieldNameList<JsonNodefoundSoFar);
    /*
    /**********************************************************
    /* Public API, path handling
    /**********************************************************
     */

    
Method that can be called on Object nodes, to access a property that has Object value; or if no such property exists, to create, add and return such Object node. If the node method is called on is not Object node, or if property exists and has value that is not Object node, java.lang.UnsupportedOperationException is thrown
    public JsonNode with(String propertyName) {
        throw new UnsupportedOperationException("JsonNode not of type ObjectNode (but "
                +getClass().getName()+"), can not call with() on it");
    }

    
Method that can be called on Object nodes, to access a property that has Array value; or if no such property exists, to create, add and return such Array node. If the node method is called on is not Object node, or if property exists and has value that is not Array node, java.lang.UnsupportedOperationException is thrown
    public JsonNode withArray(String propertyName) {
        throw new UnsupportedOperationException("JsonNode not of type ObjectNode (but "
                +getClass().getName()+"), can not call withArray() on it");
    }
    /*
    /**********************************************************
    /* Overridden standard methods
    /**********************************************************
     */
    
    

Note: marked as abstract to ensure all implementation classes define it properly.

    @Override
    public abstract String toString();

    
Equality for node objects is defined as full (deep) value equality. This means that it is possible to compare complete JSON trees for equality by comparing equality of root nodes.

Note: marked as abstract to ensure all implementation classes define it properly and not rely on definition from java.lang.Object.

    @Override
    public abstract boolean equals(Object o);
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