Util (GWT 2.7.0)

java.lang.Object
- com.google.gwt.dev.util.Util

```
public final class Util
extends Object
```
A smattering of useful methods. Methods in this class are candidates for being moved to Utility if they would be generally useful to tool writers, and don't involve TreeLogger.

Field Summary

Fields
Modifier and Type Field and Description

static String DEFAULT_ENCODING

static File[] EMPTY_ARRAY_FILE

static String[] EMPTY_ARRAY_STRING

Fields
Modifier and Type	Field and Description
`static String`	`DEFAULT_ENCODING`
`static File[]`	`EMPTY_ARRAY_FILE`
`static String[]`	`EMPTY_ARRAY_STRING`

Method Summary

All Methods Static Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`static byte[]`	`append(byte[] xs, byte x)`
`static <T> T[]`	`append(T[] xs, T x)`
`static <T> T[]`	`append(T[] appendToThis, T[] these)`
`static String`	`computeStrongName(byte[] content)` Computes the MD5 hash for the specified byte array.
`static String`	`computeStrongName(byte[][] contents)` Computes the MD5 hash of the specified byte arrays.
`static void`	`copy(InputStream is, OutputStream os)`
`static boolean`	`copy(TreeLogger logger, File in, File out)`
`static void`	`copy(TreeLogger logger, InputStream is, File out)` Copies an input stream out to a file.
`static void`	`copy(TreeLogger logger, InputStream is, OutputStream os)` Copies an input stream out to an output stream.
`static boolean`	`copy(TreeLogger logger, URL in, File out)`
`static void`	`copyNoClose(InputStream is, OutputStream os)` Copies all of the bytes from the input stream to the output stream until the input stream is EOF.
`static Reader`	`createReader(TreeLogger logger, URL url)`
`static void`	`deleteFilesInDirectory(File dir)`
`static void`	`deleteFilesStartingWith(File dir, String prefix)` Deletes all files have the same base name as the specified file.
`static boolean`	`equalsNullCheck(Object thisObject, Object thatObject)` Equality check through equals() that is also satisfied if both objects are null.
`static String`	`escapeXml(String unescaped)` Escapes '&', '<', '>', '"', and '\'' to their XML entity equivalents.
`static void`	`escapeXml(String code, int start, int end, boolean quoteApostrophe, StringBuilder builder)` Escapes '&', '<', '>', '"', and optionally ''' to their XML entity equivalents.
`static URL`	`findSourceInClassPath(ClassLoader cl, String sourceTypeName)`
`static byte[]`	`getBytes(String s)` Returns a byte-array representing the default encoding for a String.
`static byte[][]`	`getBytes(String[] s)` Returns an array of byte-arrays representing the default encoding for an array of Strings.
`static String`	`getClassName(Class<?> cls)`
`static String`	`getClassName(String className)`
`static String`	`getFileFromInstallPath(String relativePath)` Gets the contents of a file.
`static String`	`getPackageName(String qualifiedName)`
`static long`	`getResourceModifiedTime(URL url)` Retrieves the last modified time of a provided URL.
`static void`	`hex4(char c, StringBuffer sb)` Deprecated. use `StringUtils.hex4(char, StringBuffer)` instead.
`static void`	`invokeInaccessableMethod(Class<?> targetClass, String methodName, Class<?>[] argumentTypes, TypeOracle target, Object[] arguments)` This method invokes an inaccessible method in another class.
`static boolean`	`isValidJavaIdent(String token)`
`static File`	`makeRelativeFile(File from, File to)` Attempts to make a path relative to a particular directory.
`static String`	`makeRelativePath(File from, File to)`
`static String`	`makeRelativePath(File from, String to)`
`static byte[]`	`readFileAsBytes(File file)`
`static char[]`	`readFileAsChars(File file)`
`static <T extends Serializable> T`	`readFileAsObject(File file, Class<T> type)`
`static String`	`readFileAsString(File file)`
`static String`	`readNextLine(BufferedReader br)` Reads the next non-empty line.
`static byte[]`	`readStreamAsBytes(InputStream in)` Reads an entire input stream as bytes.
`static <T> T`	`readStreamAsObject(InputStream inputStream, Class<T> type)`
`static String`	`readStreamAsString(InputStream in)` Reads an entire input stream as String.
`static byte[]`	`readURLAsBytes(URL url)`
`static char[]`	`readURLAsChars(URL url)`
`static String`	`readURLAsString(URL url)`
`static byte[]`	`readURLConnectionAsBytes(URLConnection connection)`
`static void`	`recursiveDelete(File file, boolean childrenOnly)` Deletes a file or recursively deletes a directory.
`static void`	`recursiveDelete(File file, boolean childrenOnly, FileFilter filter)` Selectively deletes a file or recursively deletes a directory.
`static SortedSet<String>`	`recursiveListPartialPaths(File parent, boolean includeDirs)` Recursively lists a directory, returning the partial paths of the child files.
`static void`	`releaseThreadLocalBuf(byte[] buf)` Release a buffer previously returned from `takeThreadLocalBuf()`.
`static File`	`removeExtension(File file)`
`static <T> T[]`	`removeNulls(T[] a)`
`static String`	`slashify(String path)`
`static String`	`stripJarPathPrefix(String absolutePath)` Remove leading file:jar:...!/ prefix from source paths for source located in jars.
`static byte[]`	`takeThreadLocalBuf()` Get a large byte buffer local to this thread.
`static <T> T[]`	`toArray(Class<? super T> componentType, Collection<? extends T> coll)` Creates an array from a collection of the specified component type and size.
`static <T> T[]`	`toArrayReversed(Class<? super T> componentType, Collection<? extends T> coll)` Like `toArray(Class, Collection)`, but the option of having the array reversed.
`static String`	`toHexString(byte[] bytes)` Deprecated. use `StringUtils.toHexString(byte[])` instead.
`static String`	`toString(byte[] bytes)` Returns a String representing the character content of the bytes; the bytes must be encoded using the compiler's default encoding.
`static String[]`	`toStringArray(Collection<String> coll)` Creates a string array from the contents of a collection.
`static String[]`	`toStrings(byte[][] bytes)`
`static URL`	`toURL(File f)`
`static String`	`toXml(Document doc)`
`static byte[]`	`toXmlUtf8(Document doc)`
`static File`	`tryCombine(File parentMaybeIgnored, File childMaybeAbsolute)`
`static File`	`tryCombine(File parentMaybeIgnored, String childMaybeAbsolute)`
`static File`	`tryMakeCanonical(File file)` Attempts to find the canonical form of a file path.
`static void`	`writeBytesToFile(TreeLogger logger, File where, byte[] what)`
`static void`	`writeBytesToFile(TreeLogger logger, File where, byte[][] what)` Gathering write.
`static void`	`writeCharsAsFile(TreeLogger logger, File file, char[] chars)`
`static void`	`writeObjectAsFile(TreeLogger logger, File file, Object... objects)` Serializes an object and writes it to a file.
`static void`	`writeObjectToStream(OutputStream stream, Object... objects)` Serializes an object and writes it to a stream.
`static boolean`	`writeStringAsFile(File file, String string)`
`static void`	`writeStringAsFile(TreeLogger logger, File file, String string)`
`static void`	`writeStringToStream(OutputStream stream, String string)`
`static void`	`writeUtf8(StringBuilder builder, OutputStream out)` Writes the contents of a StringBuilder to an OutputStream, encoding each character using the UTF-* encoding.

Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, toString

Field Detail

DEFAULT_ENCODING
```
public static String DEFAULT_ENCODING
```

EMPTY_ARRAY_FILE

public static final File[] EMPTY_ARRAY_FILE

EMPTY_ARRAY_STRING

public static final String[] EMPTY_ARRAY_STRING

Method Detail

append

public static byte[] append(byte[] xs,
                            byte x)

append

public static <T> T[] append(T[] xs,
                             T x)

append

public static <T> T[] append(T[] appendToThis,
                             T[] these)

computeStrongName
```
public static String computeStrongName(byte[] content)
```
Computes the MD5 hash for the specified byte array.

Returns:

a big fat string encoding of the MD5 for the content, suitably formatted for use as a file name

computeStrongName
```
public static String computeStrongName(byte[][] contents)
```
Computes the MD5 hash of the specified byte arrays.

Returns:

a big fat string encoding of the MD5 for the content, suitably formatted for use as a file name

copy

public static void copy(InputStream is,
                        OutputStream os)
                 throws IOException

Throws:: IOException

copy

public static boolean copy(TreeLogger logger,
                           File in,
                           File out)
                    throws UnableToCompleteException

Throws:: UnableToCompleteException

copy

public static void copy(TreeLogger logger,
                        InputStream is,
                        File out)
                 throws UnableToCompleteException

Copies an input stream out to a file. Closes the input steam.

Throws:: UnableToCompleteException

copy

public static void copy(TreeLogger logger,
                        InputStream is,
                        OutputStream os)
                 throws UnableToCompleteException

Copies an input stream out to an output stream. Closes the input steam and output stream.

Throws:: UnableToCompleteException

copy

public static boolean copy(TreeLogger logger,
                           URL in,
                           File out)
                    throws UnableToCompleteException

Throws:: UnableToCompleteException

copyNoClose

public static void copyNoClose(InputStream is,
                               OutputStream os)
                        throws IOException

Copies all of the bytes from the input stream to the output stream until the input stream is EOF. Does not close either stream.

Throws:: IOException

createReader

public static Reader createReader(TreeLogger logger,
                                  URL url)
                           throws UnableToCompleteException

Throws:: UnableToCompleteException

deleteFilesInDirectory

public static void deleteFilesInDirectory(File dir)

deleteFilesStartingWith

public static void deleteFilesStartingWith(File dir,
                                           String prefix)

Deletes all files have the same base name as the specified file.

equalsNullCheck

public static boolean equalsNullCheck(Object thisObject,
                                      Object thatObject)

Equality check through equals() that is also satisfied if both objects are null.

escapeXml
```
public static String escapeXml(String unescaped)
```
Escapes '&', '<', '>', '"', and '\'' to their XML entity equivalents.

escapeXml
```
public static void escapeXml(String code,
                             int start,
                             int end,
                             boolean quoteApostrophe,
                             StringBuilder builder)
```
Escapes '&', '<', '>', '"', and optionally ''' to their XML entity equivalents. The portion of the input string between start (inclusive) and end (exclusive) is scanned. The output is appended to the given StringBuilder.

Parameters:

code - the input String

start - the first character position to scan.

end - the character position following the last character to scan.

quoteApostrophe - if true, the ' character is quoted as '

builder - a StringBuilder to be appended with the output.

findSourceInClassPath

public static URL findSourceInClassPath(ClassLoader cl,
                                        String sourceTypeName)

getBytes
```
public static byte[] getBytes(String s)
```
Returns a byte-array representing the default encoding for a String.

getBytes
```
public static byte[][] getBytes(String[] s)
```
Returns an array of byte-arrays representing the default encoding for an array of Strings.

getClassName
```
public static String getClassName(Class<?> cls)
```
Parameters:

cls - A class whose name you want.

Returns:

The base name for the specified class.

getClassName
```
public static String getClassName(String className)
```
Parameters:

className - A fully-qualified class name whose name you want.

Returns:

The base name for the specified class.

getFileFromInstallPath
```
public static String getFileFromInstallPath(String relativePath)
```
Gets the contents of a file.

Parameters:

relativePath - relative path within the install directory

Returns:

the contents of the file, or null if an error occurred

getPackageName
```
public static String getPackageName(String qualifiedName)
```
Parameters:

qualifiedName - A fully-qualified class name whose package name you want.

Returns:

The package name for the specified class, empty string if default package.

getResourceModifiedTime
```
public static long getResourceModifiedTime(URL url)
```
Retrieves the last modified time of a provided URL.

Returns:

a positive value indicating milliseconds since the epoch (00:00:00 Jan 1, 1970), or 0L on failure, such as a SecurityException or IOException.

hex4

@Deprecated
public static void hex4(char c,
                                    StringBuffer sb)

Deprecated. use StringUtils.hex4(char, StringBuffer) instead.

A 4-digit hex result.

invokeInaccessableMethod

public static void invokeInaccessableMethod(Class<?> targetClass,
                                            String methodName,
                                            Class<?>[] argumentTypes,
                                            TypeOracle target,
                                            Object[] arguments)

This method invokes an inaccessible method in another class.

Parameters:: targetClass - the class owning the method; methodName - the name of the method; argumentTypes - the types of the parameters to the method call; target - the receiver of the method call; arguments - the parameters to the method call

isValidJavaIdent

public static boolean isValidJavaIdent(String token)

makeRelativeFile
```
public static File makeRelativeFile(File from,
                                    File to)
```
Attempts to make a path relative to a particular directory.

Parameters:

from - the directory from which 'to' should be relative

to - an absolute path which will be returned so that it is relative to 'from'

Returns:

the relative path, if possible; null otherwise

makeRelativePath

public static String makeRelativePath(File from,
                                      File to)

makeRelativePath

public static String makeRelativePath(File from,
                                      String to)

readFileAsBytes

public static byte[] readFileAsBytes(File file)

readFileAsChars

public static char[] readFileAsChars(File file)

readFileAsObject

public static <T extends Serializable> T readFileAsObject(File file,
                                                          Class<T> type)
                                                   throws ClassNotFoundException,
                                                          IOException

Throws:: ClassNotFoundException; IOException

readFileAsString

public static String readFileAsString(File file)

readNextLine
```
public static String readNextLine(BufferedReader br)
```
Reads the next non-empty line.

Returns:

a non-empty string that has been trimmed or null if the reader is exhausted

readStreamAsBytes
```
public static byte[] readStreamAsBytes(InputStream in)
```
Reads an entire input stream as bytes. Closes the input stream.

readStreamAsObject

public static <T> T readStreamAsObject(InputStream inputStream,
                                       Class<T> type)
                                throws ClassNotFoundException,
                                       IOException

Throws:: ClassNotFoundException; IOException

readStreamAsString
```
public static String readStreamAsString(InputStream in)
```
Reads an entire input stream as String. Closes the input stream.

readURLAsBytes
```
public static byte[] readURLAsBytes(URL url)
```
Returns:

null if the file could not be read

readURLAsChars
```
public static char[] readURLAsChars(URL url)
```
Returns:

null if the file could not be read

readURLAsString
```
public static String readURLAsString(URL url)
```
Returns:

null if the file could not be read

readURLConnectionAsBytes

public static byte[] readURLConnectionAsBytes(URLConnection connection)

recursiveDelete
```
public static void recursiveDelete(File file,
                                   boolean childrenOnly)
```
Deletes a file or recursively deletes a directory.

Parameters:

file - the file to delete, or if this is a directory, the directory that serves as the root of a recursive deletion

childrenOnly - if true, only the children of a directory are recursively deleted but the specified directory itself is spared; if false, the specified directory is also deleted; ignored if file is not a directory

recursiveDelete
```
public static void recursiveDelete(File file,
                                   boolean childrenOnly,
                                   FileFilter filter)
```
Selectively deletes a file or recursively deletes a directory. Note that it is possible that files remain if file.delete() fails.

Parameters:

file - the file to delete, or if this is a directory, the directory that serves as the root of a recursive deletion

childrenOnly - if true, only the children of a directory are recursively deleted but the specified directory itself is spared; if false, the specified directory is also deleted; ignored if file is not a directory

filter - only files matching this filter will be deleted

recursiveListPartialPaths
```
public static SortedSet<String> recursiveListPartialPaths(File parent,
                                                          boolean includeDirs)
```
Recursively lists a directory, returning the partial paths of the child files.

Parameters:

parent - the directory to start from

includeDirs - whether or not to include directories in the results

Returns:

all partial paths descending from the parent file

releaseThreadLocalBuf
```
public static void releaseThreadLocalBuf(byte[] buf)
```
Release a buffer previously returned from takeThreadLocalBuf(). The released buffer may then be reused.

removeExtension

public static File removeExtension(File file)

removeNulls

public static <T> T[] removeNulls(T[] a)

slashify
```
public static String slashify(String path)
```
Parameters:

path - The path to slashify.

Returns:

The path with any directory separators replaced with '/'.

stripJarPathPrefix
```
public static String stripJarPathPrefix(String absolutePath)
```
Remove leading file:jar:...!/ prefix from source paths for source located in jars.

Parameters:

absolutePath - an absolute JAR file URL path

Returns:

the location of the file within the JAR

takeThreadLocalBuf
```
public static byte[] takeThreadLocalBuf()
```
Get a large byte buffer local to this thread. Currently this is set to a 16k buffer, which is small enough to fit into the L2 cache on modern processors. The contents of the returned buffer are undefined. Calling releaseThreadLocalBuf(byte[]) on the returned buffer allows subsequent callers to reuse the buffer later, avoiding unncessary allocations and GC.

toArray
```
public static <T> T[] toArray(Class<? super T> componentType,
                              Collection<? extends T> coll)
```
Creates an array from a collection of the specified component type and size. You can definitely downcast the result to T[] if T is the specified component type. Class is used to allow creation of generic types, such as Map.Entry since we can only pass in Map.Entry.class.

toArrayReversed

public static <T> T[] toArrayReversed(Class<? super T> componentType,
                                      Collection<? extends T> coll)

Like toArray(Class, Collection), but the option of having the array reversed.

toHexString
```
@Deprecated
public static String toHexString(byte[] bytes)
```
Deprecated. use StringUtils.toHexString(byte[]) instead.

Returns a string representation of the byte array as a series of hexadecimal characters.

Parameters:

bytes - byte array to convert

Returns:

a string representation of the byte array as a series of hexadecimal characters

toString
```
public static String toString(byte[] bytes)
```
Returns a String representing the character content of the bytes; the bytes must be encoded using the compiler's default encoding.

toStringArray
```
public static String[] toStringArray(Collection<String> coll)
```
Creates a string array from the contents of a collection.

toStrings

public static String[] toStrings(byte[][] bytes)

toURL
```
public static URL toURL(File f)
```

toXml

public static String toXml(Document doc)

toXmlUtf8

public static byte[] toXmlUtf8(Document doc)

tryCombine

public static File tryCombine(File parentMaybeIgnored,
                              File childMaybeAbsolute)

tryCombine

public static File tryCombine(File parentMaybeIgnored,
                              String childMaybeAbsolute)

tryMakeCanonical
```
public static File tryMakeCanonical(File file)
```
Attempts to find the canonical form of a file path.

Returns:

the canonical version of the file path, if it could be computed; otherwise, the original file is returned unmodified

writeBytesToFile

public static void writeBytesToFile(TreeLogger logger,
                                    File where,
                                    byte[] what)
                             throws UnableToCompleteException

Throws:: UnableToCompleteException

writeBytesToFile

public static void writeBytesToFile(TreeLogger logger,
                                    File where,
                                    byte[][] what)
                             throws UnableToCompleteException

Gathering write.

Throws:: UnableToCompleteException

writeCharsAsFile

public static void writeCharsAsFile(TreeLogger logger,
                                    File file,
                                    char[] chars)
                             throws UnableToCompleteException

Throws:: UnableToCompleteException

writeObjectAsFile

public static void writeObjectAsFile(TreeLogger logger,
                                     File file,
                                     Object... objects)
                              throws UnableToCompleteException

Serializes an object and writes it to a file.

Throws:: UnableToCompleteException

writeObjectToStream

public static void writeObjectToStream(OutputStream stream,
                                       Object... objects)
                                throws IOException

Serializes an object and writes it to a stream.

Throws:: IOException

writeStringAsFile

public static boolean writeStringAsFile(File file,
                                        String string)

writeStringAsFile

public static void writeStringAsFile(TreeLogger logger,
                                     File file,
                                     String string)
                              throws UnableToCompleteException

Throws:: UnableToCompleteException

writeStringToStream

public static void writeStringToStream(OutputStream stream,
                                       String string)
                                throws IOException

Throws:: IOException

writeUtf8
```
public static void writeUtf8(StringBuilder builder,
                             OutputStream out)
                      throws IOException
```
Writes the contents of a StringBuilder to an OutputStream, encoding each character using the UTF-* encoding. Unicode characters between U+0000 and U+10FFFF are supported.

Throws:

IOException

Class Util

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

DEFAULT_ENCODING

EMPTY_ARRAY_FILE

EMPTY_ARRAY_STRING

Method Detail

append

append

append

computeStrongName

computeStrongName

copy

copy

copy

copy

copy

copyNoClose

createReader

deleteFilesInDirectory

deleteFilesStartingWith

equalsNullCheck

escapeXml

escapeXml

findSourceInClassPath

getBytes

getBytes

getClassName

getClassName

getFileFromInstallPath

getPackageName

getResourceModifiedTime

hex4

invokeInaccessableMethod

isValidJavaIdent

makeRelativeFile

makeRelativePath

makeRelativePath

readFileAsBytes

readFileAsChars

readFileAsObject

readFileAsString

readNextLine

readStreamAsBytes

readStreamAsObject

readStreamAsString

readURLAsBytes

readURLAsChars

readURLAsString

readURLConnectionAsBytes

recursiveDelete

recursiveDelete

recursiveListPartialPaths

releaseThreadLocalBuf

removeExtension

removeNulls

slashify

stripJarPathPrefix

takeThreadLocalBuf

toArray

toArrayReversed

toHexString

toString

toStringArray

toStrings

toURL

toXml

toXmlUtf8

tryCombine

tryCombine

tryMakeCanonical

writeBytesToFile

writeBytesToFile

writeCharsAsFile

writeObjectAsFile

writeObjectToStream

writeStringAsFile

writeStringAsFile