Java Module jdk.httpserver Package com.sun.net.httpserver Class Headers（JDK11）

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java.lang.Object
- com.sun.net.httpserver.Headers

All Implemented Interfaces:

Map<String,List<String>>
```
public class Headers
extends Object
implements Map<String,List<String>>
```
HTTP request and response headers are represented by this class which implements the interface Map<String, List <String>>. The keys are case-insensitive Strings representing the header names and the value associated with each key is a List<String> with one element for each occurrence of the header name in the request or response.
For example, if a response header instance contains one key "HeaderName" with two values "value1 and value2" then this object is output as two header lines:
```
 HeaderName: value1
 HeaderName: value2
 
```
All the normal Map methods are provided, but the following additional convenience methods are most likely to be used:
- getFirst(String) returns a single valued header or the first value of a multi-valued header.
- add(String,String) adds the given header value to the list for the given key
- set(String,String) sets the given header field to the single value given overwriting any existing values in the value list.
All methods in this class accept null values for keys and values. However, null keys will never will be present in HTTP request headers, and will not be output/sent in response headers. Null values can be represented as either a null entry for the key (i.e. the list is null) or where the key has a list, but one (or more) of the list's values is null. Null values are output as a header line containing the key but no associated value.
Since:

1.6

Nested Class Summary
- Nested classes/interfaces declared in interface java.util.Map
  Map.Entry<K,V>

Constructor Summary

Constructors
Constructor	Description
`Headers()`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`add(String key, String value)`	adds the given value to the list of headers for the given key.
`String`	`getFirst(String key)`	returns the first value from the List of String values for the given key (if at least one exists).
`void`	`set(String key, String value)`	sets the given value as the sole header value for the given key.

Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods declared in interface java.util.Map
clear, compute, computeIfAbsent, computeIfPresent, containsKey, containsValue, entrySet, equals, forEach, get, getOrDefault, hashCode, isEmpty, keySet, merge, put, putAll, putIfAbsent, remove, remove, replace, replace, replaceAll, size, values

- Constructor Detail
  - Headers
```
public Headers()
```
- Method Detail
  - getFirst
```
public String getFirst(String key)
```
    returns the first value from the List of String values for the given key (if at least one exists).
    
    Parameters:
    
    key - the key to search for
    
    Returns:
    
    the first string value associated with the key
  - add
```
public void add(String key,
                String value)
```
    adds the given value to the list of headers for the given key. If the mapping does not already exist, then it is created
    
    Parameters:
    
    key - the header name
    
    value - the header value to add to the header
  - set
```
public void set(String key,
                String value)
```
    sets the given value as the sole header value for the given key. If the mapping does not already exist, then it is created
    
    Parameters:
    
    key - the header name
    
    value - the header value to set.

Java Module jdk.httpserver Package com.sun.net.httpserver Class Headers（JDK11）

Class Headers

Nested Class Summary

Nested classes/interfaces declared in interface java.util.Map

Constructor Summary

Method Summary

Methods declared in class java.lang.Object

Methods declared in interface java.util.Map

Constructor Detail

Headers

Method Detail

getFirst

add

set