public class URLEncoder
extends Object



Utility class for HTML form encoding. This class contains static methods for converting a String to the application/x-www-form-urlencoded MIME format. For more information about HTML form encoding, consult the HTML specification.

When encoding a String, the following rules apply:

  • The alphanumeric characters "a" through "z", "A" through "Z" and "0" through "9" remain the same.
  • The special characters ".", "-", "*", and "_" remain the same.
  • The space character "   " is converted into a plus sign "+".
  • All other characters are unsafe and are first converted into one or more bytes using some encoding scheme. Then each byte is represented by the 3-character string "%xy", where xy is the two-digit hexadecimal representation of the byte. The recommended encoding scheme to use is UTF-8. However, for compatibility reasons, if an encoding is not specified, then the default encoding of the platform is used.

For example using UTF-8 as the encoding scheme the string "The string ü@foo-bar" would get converted to "The+string+%C3%BC%40foo-bar" because in UTF-8 the character ü is encoded as two bytes C3 (hex) and BC (hex), and the character @ is encoded as one byte 40 (hex).

Summary

Public methods

static String encode(String s, String enc)

Translates a string into application/x-www-form-urlencoded format using a specific encoding scheme.

static String encode(String s)

This method was deprecated in API level 15. The resulting string may vary depending on the platform's default encoding. Instead, use the encode(String,String) method to specify the encoding.

static String encode(String s, Charset charset)

Translates a string into application/x-www-form-urlencoded format using a specific Charset.

Inherited methods

From class java.lang.Object

Object clone()

Creates and returns a copy of this object.

boolean equals(Object obj)

Indicates whether some other object is "equal to" this one.

void finalize()

Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.

final Class<?> getClass()

Returns the runtime class of this Object.

int hashCode()

Returns a hash code value for the object.

final void notify()

Wakes up a single thread that is waiting on this object's monitor.

final void notifyAll()

Wakes up all threads that are waiting on this object's monitor.

String toString()

Returns a string representation of the object.

final void wait(long timeoutMillis, int nanos)

Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

final void wait(long timeoutMillis)

Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

final void wait()

Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public methods

encode

public static String encode (String s)

This method was deprecated in API level 15.
The resulting string may vary depending on the platform's default encoding. Instead, use the encode(String,String) method to specify the encoding.

Translates a string into x-www-form-urlencoded format. This method uses the platform's default encoding as the encoding scheme to obtain the bytes for unsafe characters.

Parameters
s String: String to be translated.
Returns
String the translated String.

encode

public static String encode (String s, 
                Charset charset)

Translates a string into application/x-www-form-urlencoded format using a specific Charset. This method uses the supplied charset to obtain the bytes for unsafe characters.

Note: The World Wide Web Consortium Recommendation states that UTF-8 should be used. Not doing so may introduce incompatibilities.

Parameters
s String: String to be translated.
charset Charset: the given charset
Returns
String the translated String.
Throws
NullPointerException if s or charset is null.

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Last updated 2026-02-26 UTC.