Package jakarta.json

Interface JsonArray

All Superinterfaces:
Collection<JsonValue>, Iterable<JsonValue>, JsonStructure, JsonValue, List<JsonValue>, SequencedCollection<JsonValue>
public interface JsonArray extends JsonStructure, List<JsonValue>
JsonArray represents an immutable JSON array (an ordered sequence of zero or more values). It also provides an unmodifiable list view of the values in the array.

A JsonArray object can be created by reading JSON data from an input source or it can be built from scratch using an array builder object.

The following example demonstrates how to create a JsonArray object from an input source using the method JsonReader.readArray(): 


 JsonReader jsonReader = Json.createReader(...);
 JsonArray array = jsonReader.readArray();
 jsonReader.close();

The following example demonstrates how to build an empty JSON array using the class JsonArrayBuilder: 


 JsonArray array = Json.createArrayBuilder().build();

The example code below demonstrates how to create the following JSON array: 


 [
     { "type": "home", "number": "212 555-1234" },
     { "type": "fax", "number": "646 555-4567" }
 ]
 

 JsonArray value = Json.createArrayBuilder()
     .add(Json.createObjectBuilder()
         .add("type", "home")
         .add("number", "212 555-1234"))
     .add(Json.createObjectBuilder()
         .add("type", "fax")
         .add("number", "646 555-4567"))
     .build();

The following example demonstrates how to write a JsonArray object as JSON data: 


 JsonArray arr = ...;
 JsonWriter writer = Json.createWriter(...)
 writer.writeArray(arr);
 writer.close();

The values in a JsonArray can be of the following types: JsonObject, JsonArray, JsonString, JsonNumber, JsonValue.TRUE, JsonValue.FALSE, and JsonValue.NULL. JsonArray provides various accessor methods to access the values in an array.

The following example shows how to obtain the home phone number "212 555-1234" from the array built in the previous example: 


 JsonObject home = array.getJsonObject(0);
 String number = home.getString("number");

JsonArray instances are list objects that provide read-only access to the values in the JSON array. Any attempt to modify the list, whether directly or using its collection views, results in an UnsupportedOperationException.

  • Method Details

    • getJsonObject

      JsonObject getJsonObject(int index)
      Returns the object value at the specified position in this array. This is a convenience method for (JsonObject)get(index).
      Parameters:
      index - index of the value to be returned
      Returns:
      the value at the specified position in this array
      Throws:
      IndexOutOfBoundsException - if the index is out of range
      ClassCastException - if the value at the specified position is not assignable to the JsonObject type

    • getJsonArray

      JsonArray getJsonArray(int index)
      Returns the array value at the specified position in this array. This is a convenience method for (JsonArray)get(index).
      Parameters:
      index - index of the value to be returned
      Returns:
      the value at the specified position in this array
      Throws:
      IndexOutOfBoundsException - if the index is out of range
      ClassCastException - if the value at the specified position is not assignable to the JsonArray type

    • getJsonNumber

      JsonNumber getJsonNumber(int index)
      Returns the number value at the specified position in this array. This is a convenience method for (JsonNumber)get(index).
      Parameters:
      index - index of the value to be returned
      Returns:
      the value at the specified position in this array
      Throws:
      IndexOutOfBoundsException - if the index is out of range
      ClassCastException - if the value at the specified position is not assignable to the JsonNumber type

    • getJsonString

      JsonString getJsonString(int index)
      Returns the string value at ths specified position in this array. This is a convenience method for (JsonString)get(index).
      Parameters:
      index - index of the value to be returned
      Returns:
      the value at the specified position in this array
      Throws:
      IndexOutOfBoundsException - if the index is out of range
      ClassCastException - if the value at the specified position is not assignable to the JsonString type

    • getValuesAs

      <T extends JsonValue> List<T> getValuesAs(Class<T> clazz)
      Returns a list view of the specified type for the array. This method does not verify if there is a value of wrong type in the array. Providing this typesafe view dynamically may cause a program fail with a ClassCastException, if there is a value of wrong type in this array. Unfortunately, the exception can occur at any time after this method returns.
      Type Parameters:
      T - The type of the List for the array
      Parameters:
      clazz - a JsonValue type
      Returns:
      a list view of the specified type

    • getValuesAs

      default <T, K extends JsonValue> List<T> getValuesAs(Function<K,T> func)
      Returns a list view for the array. The value and the type of the elements in the list is specified by the func argument.

      This method can be used to obtain a list of the unwrapped types, such as 

      
     List<String> strings = ary1.getValuesAs(JsonString::getString);
     List<Integer> ints = ary2.getValuesAs(JsonNumber::intValue);
      or a list of simple projections, such as 
       
     List<Integer> stringsizes = ary1.getValueAs((JsonString v)->v.getString().length();
      Type Parameters:
      T - The element type of the returned List
      K - The element type (must be a subtype of JsonValue) of this JsonArray.
      Parameters:
      func - The function that maps the elements of this JsonArray to the target elements.
      Returns:
      A List of the specified values and type.
      Throws:
      ClassCastException - if the JsonArray contains a value of wrong type
      Since:
      1.1

    • getString

      String getString(int index)
      A convenience method for getJsonString(index).getString().
      Parameters:
      index - index of the JsonString value
      Returns:
      the String value at the specified position
      Throws:
      IndexOutOfBoundsException - if the index is out of range
      ClassCastException - if the value at the specified position is not assignable to JsonString

    • getString

      String getString(int index, String defaultValue)
      Returns the String value of JsonString at the specified position in this JSON array values. If JsonString is found, its JsonString.getString() is returned. Otherwise, the specified default value is returned.
      Parameters:
      index - index of the JsonString value
      defaultValue - the String to return if the JsonValue at the specified position is not a JsonString
      Returns:
      the String value at the specified position in this array, or the specified default value

    • getInt

      int getInt(int index)
      A convenience method for getJsonNumber(index).intValue().
      Parameters:
      index - index of the JsonNumber value
      Returns:
      the int value at the specified position
      Throws:
      IndexOutOfBoundsException - if the index is out of range
      ClassCastException - if the value at the specified position is not assignable to JsonNumber

    • getInt

      int getInt(int index, int defaultValue)
      Returns the int value of the JsonNumber at the specified position. If the value at that position is a JsonNumber, this method returns JsonNumber.intValue(). Otherwise this method returns the specified default value.
      Parameters:
      index - index of the JsonNumber value
      defaultValue - the int value to return if the JsonValue at the specified position is not a JsonNumber
      Returns:
      the int value at the specified position in this array, or the specified default value

    • getBoolean

      boolean getBoolean(int index)
      Returns the boolean value at the specified position. If the value at the specified position is JsonValue.TRUE this method returns true. If the value at the specified position is JsonValue.FALSE this method returns false.
      Parameters:
      index - index of the JSON boolean value
      Returns:
      the boolean value at the specified position
      Throws:
      IndexOutOfBoundsException - if the index is out of range
      ClassCastException - if the value at the specified position is not JsonValue.TRUE or JsonValue.FALSE

    • getBoolean

      boolean getBoolean(int index, boolean defaultValue)
      Returns the boolean value at the specified position. If the value at the specified position is JsonValue.TRUE this method returns true. If the value at the specified position is JsonValue.FALSE this method returns false. Otherwise this method returns the specified default value.
      Parameters:
      index - index of the JSON boolean value
      defaultValue - the boolean value to return if the JsonValue at the specified position is neither TRUE nor FALSE
      Returns:
      the boolean value at the specified position, or the specified default value

    • isNull

      boolean isNull(int index)
      Returns true if the value at the specified location in this array is JsonValue.NULL.
      Parameters:
      index - index of the JSON null value
      Returns:
      return true if the value at the specified location is JsonValue.NULL, otherwise false
      Throws:
      IndexOutOfBoundsException - if the index is out of range