File could do it by looking at a few samples. Scanner and Formatterand C-like printf and format methods for formatted output using format specifiers. It also introduces a new try bankruptcy syntax to simplify the coding of close method. File can represent either a file or a directory. Pathwhich overcomes many limitations of java. A path string is used to locate a file or a directory. Unfortunately, path strings are system dependent, e. A path could be absolute beginning from the root or relative which is relative to a reference directory. File class maintains these system-dependent properties, for you to write programs that bankruptcy portable:. You can construct a File instance with a path string or URI, as output. A file URL takes the form of file: For applications that you intend to distribute as JAR files, you should use the URL class to reference the resources, as it can reference disk files as well as JAR'ed filesfor example. The following program recursively lists the contents of a given directory similar to Unix's "ls -r" command. You can apply a filter to list and listFilesto list only files that meet a certain criteria. FilenameFilter declares one abstract method:. You bankruptcy program your filtering criteria in accept. The following program lists only files that meet a certain filtering criteria. Programs read inputs from data sources e. A stream is a sequential and contiguous one-way flow of data just like water or oil flows through the pipe. It is important to mention that Java does not differentiate between the various types of data sources or sinks e. They are all treated as a sequential flow of data. The Java program receives data from a source by opening an input stream, and sends data options a sink by opening an output stream. If your program needs to perform both input and output, you have to open two streams - an input stream and an output stream. Java internally stores characters char type in bit UCS-2 character set. All the byte streams are derived from the file superclasses InputStream and OutputStreamas illustrated in the class diagram. The abstract superclass InputStream declares an abstract method read to read one data-byte from the input source:. The read method returns an int file of a bytebecause it uses -1 to indicate end-of-stream. The term " block " means that the method and the program will be suspended. The program will resume only when the method returns. Two variations of read methods are implemented in the InputStream for reading a block of native2ascii into a byte-array. It returns file number of bytes read, or -1 if "end-of-stream" encounters. Similar to the input counterpart, the abstract superclass OutputStream declares an abstract method write to write a data-byte to the output sink. The least-significant byte of the int argument is written out; the upper 3 bytes are discarded. Similar to the readtwo variations of the write method to write a block of bytes from a file are implemented:. Bankruptcy the InputStream and the OutputStream provides output close method to close the stream, which performs the necessary clean-up operations to free up the system resources. This could prevent serious resource leaks. Unfortunately, the close method also throws a IOExceptionand needs to be enclosed in a nested try-catch statement, as follows. This makes the codes somehow ugly. This produces much neater codes. In addition, the OutputStream provides a flush method to flush the remaining bytes from the output buffer. InputStream and OutputStream are abstract classes that cannot be instantiated. You need to choose an appropriate concrete subclass to establish a connection to a physical device. For example, you can instantiate a FileInputStream or FileOutputStream to establish a stream to a physical disk file. For example, we can layer a BufferedInputStream to a FileInputStream for buffered input, and stack a DataInputStream in front for formatted data output using primitives such as intdoubleas illustrated in the following diagrams. This is grossly inefficient, as each call is handled by the underlying operating system which may trigger a disk access, or other expensive operations. It is often chained file a BufferedInputStream or BufferedOutputStreamwhich provides the buffering. To chain the streams together, simply pass an instance of one stream into the constructor of another stream. For example, the following codes chain a FileInputStream to a BufferedInputStreamand finally, a DataInputStream:. This example copies a file by reading a byte from the input file and writing it to the output file. It uses FileInputStream output FileOutputStream directly without buffering. The method close is programmed inside the finally clause. It is guaranteed to be run after try or input. However, method close also throws an IOExceptionand therefore must be enclosed inside a nested try-catch block, which makes the codes a little ugly. The output shows that it took about 4 seconds to copy a KB file. As mentioned, JDK 1. For example, the above example can be re-written in options much neater manner as follow:. This example again uses FileInputStream and FileOutputStream directly. This program took bankruptcy 3 millisecond - a more than times speed-up compared with the previous example. However, there is a trade-off input speed-up the the memory usage. Options file copying, a large native2ascii is certainly recommended. But for reading just a few bytes from a file, large buffer simply wastes the memory. I re-write the program using JDK 1. The JRE decides on the buffer size. The program took 62 milliseconds, about 60 times speed-up compared with example 1, but slower than the programmer-managed buffer. To use DataInputStream for formatted input, file can chain up the input streams as follows:. DataInputStream implements DataInput interface, which provides methods to read formatted primitive data and Stringsuch as:. DataOutputStream implements DataOutput interface, which provides methods to write formatted primitive bankruptcy and String. The following program writes some primitives to a disk file. It then reads native2ascii raw bytes to check how the primitives were stored. Finally, it reads the data as primitives. The data stored in the disk are exactly in the same form as output the Java program internally e. The byte-order is big-endian big byte first, or most significant byte in lowest address. If this character is to be written to a file uses UTF-8, the character stream needs to translate " 60 A8 " to " E6 82 A8 ". The reserve takes place in a reading operation. This is because some charsets use fixed-length of 8-bit e. When a character stream is used to read an 8-bit ASCII file, an 8-bit data is read from the file file put into the bit char location of the Java program. The abstract superclass Reader operates on char. It declares an abstract method read to read one character from the input source. There are also two variations of read to read a block of characters into char -array. The abstract superclass Writer declares an abstract method writewhich writes a character to the output sink. The lower 2 bytes of the int argument is written out; while the upper 2 bytes are discarded. The default charset is kept in the JVM's system bankruptcy " file. You can get the default charset via static method java. BufferedReader provides a new method readLinewhich reads a line and returns a String without the line delimiter. The main class java. Charset provides static methods for testing whether a particular charset is supported, locating charset instances by name, and listing all the available input and the default charset. The default charset for file encoding is kept in the system property " file. To change the JVM's default charset for file encoding, native2ascii can use command-line VM option " -Dfile. For example, the following command run the program with default charset of UTF The following example encodes some Unicode texts in various encoding scheme, and display the Hex output of the encoded byte sequences. As mentioned, Java internally stores characters char type in bit UCS-2 character set. To choose the charset, you need to use InputStreamReader and OutputStreamWriter. InputStreamReader and OutputStreamWriter are considered to be byte-to-character "bridge" streams. You can list the available charsets via static method java. The commonly-used Charset names supported by Java are:. The following input writes Unicode texts to a disk file using various charsets for file encoding. It then reads the file byte-by-byte via a byte-based input stream to check the encoded characters in the various charsets. Finally, it reads the file using the character-based reader. Nonetheless, the InputStreamReader is able to translate the file into the same UCS-2 output in Java program. Primitives are converted to their string representation for printing. The printf and format were introduced in JDK 1. A PrintStream never throws an IOException. Instead, it sets an internal flag which can be checked via the checkError method. A PrintStream can also be created to flush the output automatically. The standard output and error streams System. All characters printed by a PrintStream are converted into file using the default character encoding. The PrintWriter class should be used in situations that require writing characters rather than bytes. The character-stream PrintWriter is similar to PrintStream file, except that it write in characters instead of bytes. The PrintWriter also supports all the convenient printing methods printprintlnprintf and format. It never throws an IOException and can optionally be created to support automatic flushing. Data streams DataInputStream and DataOutputStream allow you to read and write primitive output such as intdouble and Stringrather than individual bytes. Object streams ObjectInputStream and ObjectOutputStream go one step further to allow you to read and write entire objects such as DateArrayList or any custom objects. Object serialization is the process of representing a "particular state of an object" in a serialized bit-stream, so that the bit stream can be written out to an external device such as a disk file or network. The bit-stream can later be re-constructed to recover the state of that object. Object serialization is necessary to save a state of an object into a disk file for persistence or sent the object across the network for applications such as Web Services, Distributed-object applications, and Remote Method Invocation RMI. In Java, object that requires to be serialized must implement java. Serializable interface is an empty interface or tagged interface with nothing declared. Its purpose is simply to declare that particular object is serializable. ObjectInputStream and ObjectOutputStream must be stacked on top native2ascii a concrete implementation of InputStream or OutputStreamsuch as FileInputStream or FileOutputStream. For example, the following code segment writes objects to a disk file. To read and re-construct the object back in a program, use the method readObjectwhich returns an java. Downcast the Object back to its original type. The ObjectInputStream and ObjectOutputStream implement DataInput and DataOutput interface respectively. You can used methods such as readIntreadDoublewriteIntwriteDouble for reading and writing primitive types. When you create a class that might be serialized, the class must implement java. The Serializable interface doesn't declare any methods. Empty interfaces such as Serializable are known as tagging interfaces. They identify implementing classes as having certain properties, without requiring those classes to actually implement any methods. Most of the core Java classes implement Serializablesuch as all the wrapper classes, collection classes, and GUI classes. In fact, the only core Java classes that do not implement Serializable are ones that should not be serialized. Arrays of primitives or serializable objects are themselves serializable. This warning message is triggered because your class such as java. JFrame implements the java. This interface enables the object to be written out to an output stream serially via method writeObject ; and read back into the program via method readObject. The serialization runtime uses a number called serialVersionUID to ensure that the object read into the program during deserialization is compatible with the class definition, and not belonging to another version. It throws an InvalidClassException otherwise. The Serializable has a sub-interface called Externalizablewhich you could used if you want to customize the way a class is serialized. Since Externalizable extends Serializableit is also a Serializable and you could invoke readObject and writeObject. ObjectOutput and ObjectInput input interfaces that are implemented by ObjectOutputStream and ObjectInputStreamwhich define the writeObject and readObject methods, respectively. When an instance of Externalizable is passed to an ObjectOutputStreamthe default serialization procedure is bypassed; instead, the stream calls the instance's writeExternal method. Similarly, when an ObjectInputStream reads a Exteranlizabled instance, it uses readExternal to reconstruct the instance. For example, you could encrypt sensitive data before the object is serialized. That is, they are either read-only output stream or write-only output stream. Furthermore, they are all sequential-access or serial streams, meant for reading and writing data sequentially. Nonetheless, it is sometimes necessary to read a file record directly options well as modifying existing records or inserting new records. The class RandomAccessFile provides supports for non-sequential, direct or random access to a disk file. RandomAccessFile is a native2ascii stream, supporting both input and output operations in the same stream. RandomAccessFile can be treated as a huge byte array. You can use a file pointer of type longsimilar to array index, to access individual byte or group of bytes in primitive types such as int and double. The file pointer is located at 0 when the file is opened. It advances automatically for every read and write operation by the number of bytes processed. In constructing a RandomAccessFileyou can use options 'r' or 'rw' to indicate whether the file is "read-only" or "read-write" access, e. RandomAccessFile does not inherit from InputStream or OutputStream. However, it implements DataInput and DataOutput interfaces similar to DataInputStream and DataOutputStream. Read and write records from a RandomAccessFile. A student file consists of student record of name String file id int. The classes ZipInputStream and ZipOutputStream in package java. The classes GZIPInputStream and GZIPOutputStream in package java. Scanner class, which greatly simplifies formatted text input from input source e. Scanneras the name implied, is a simple text scanner which can parse the input text into primitive types and strings using regular expressions. It first breaks the text input into tokens using a delimiter pattern, which is by default the white spaces blank, tab and newline. File tokens may then be converted into primitive values of different types using the various nextXxx methods nextIntnextBytenextShortnextLongnextFloatnextDoublenextBooleannext for Stringand nextLine for an input options. You can also use the hasNextXxx methods to check for the availability of a bankruptcy input. The commonly-used constructors are as follows. You can construct a Scanner to parse a byte-based InputStream e. The most common usage of Scanner is to read primitive types and String form the keyboard System. The nextXxx methods throw InputMismatchException if the next token does not match the type to be parsed. You can output modify the above program to read the inputs from a text file, instead of keyboard System. You can file hasNext coupled with next to file through all the String tokens. You can also directly iterate through file primitive types via methods hasNextXxx and nextXxx. Xxx includes all primitive types byteshortintlongfloat options, double and booleanBigInteger, and BigNumber. Instead of the default white spaces as the delimiter, you can set the delimiter to a chosen regular expression via bankruptcy methods:. Read " Regular Expression " for more details. You can use the following methods to find the next occurrence of the specified pattern using regular expressions:. By default, Scanner uses the default charset to read the character input the input source. You can ask Scanner to read text file which is encoded using a particular charset, by providing the charset name. PrintWriter for input printing. To write formatted-text to console System. Varargs was introduced in JDK 1. You can also use the System. Read JDK API java. Formatter 's " Format String Syntax " for details on format specifiers. Scanner for formatted text input. It also options java. Formatter for formatted text output. A Formatter is an interpreter for printf -style format strings. It does not support Stringprobably because String is immutable. Notice that the method format has the same syntax as the method printfusing the same set of format specifier as printf. Using a StringBuilder which implements Appendable as the output sink for the Formatter. Setting the charset for Formatter 's output. The Formatter with StringBuilder as the output sink allows you to build up a formatted string progressively. To produce a simple formatted Stringyou can simply use the static method String. This is handy in the toString method, which is required to return a String. A path string could be used to locate a filea directory or a symbolic link. A symbolic link or symlink is a special file that references another file. A path string is system dependent, e. Windows uses semi-colon ';' as path separator; while Unixes input colon ': Windows supports multiple roots, each maps to a drive e. A path could be absolute beginning from the root or relative which is relative to the current working directory. Path instance specifies the location of a file, or a directory, or a symbolic link. To create a Pathuse the static method get of the helper class java. The helper class Paths contains exclusively static methods for creating Path objects. As the directory-separator is system dependent, for writing portable and more flexible program, it is recommended to use an existing Path instance as an anchor to resolve the filename, e. A File can be broken down as root, level-0, level-1, The method getNameCount returns the levels. The method getName i returns the name of level-i. The class Files contains exclusively static methods for file, directory and symlink operations such as create, delete, read, write, copy, move, etc. You can use static boolean methods Files. A Path could be verified to exist, or not exist, or unknown e. Bankruptcy the status is unknown, the exists and noExists returns false. You could also use static boolean methods Files. Many of these methods take an optional second argument of LinkOptionwhich is applicable for symlink only. You can use static methods delete Path to delete a file or directory. Directory can be deleted only if it is empty. A boolean method deleteIfExists file also available. You can use static methods copy Path, Path, CopyOption file move Path, Path, CopyOption to copy or move a file or directory. The methods return the target Path. The methods accepts an optional third argument of CopyOption. For small files, you can use static methods Files. You can use Files. The optional OpenOption includes: The following example write a small text file in "UTF-8"and read the entire file back as bytes as well as characters. For Reading, use Files. For Writing, use the Files. The InputStream and OutputStream returned are not buffered. Beside using the Files. You can use the default file attributes or optionally define the initial attributes of the file. You can use one of the Files. You can list the contents of a directory by using the Files. The returned DirectoryStream object implements Iterable. You can bankruptcy thru the entries with for-each loop. Those entries that resulted in false accept will be discarded. The following program uses an anonymous instance of an anonymous DirectoryStream. Filter sub-class to filter the DirectoryStream. The call-back method accept returns true for regular files, and discards the rest. Take note that this filtering criterion native2ascii be implemented in a glob-pattern. You can use static method Files. Instead of implementing FileVisitor interface, you could also extend from superclass SimpleFileVisitorand override the selected methods. There are two versions of walkFileTree. The first version take a starting directory and a FileVisitorand transverse through all the levels, without following the symlinks. File second version takes 2 additional arguments: TABLE OF CONTENTS HIDE. File and Directory Class java. File Pre-JDK 7 The class java. File class maintains these system-dependent properties, for you to write programs that file portable: List Directory For a directory, you can use the following methods to list its contents: FilenameFilter declares one abstract method: Read from the opened input stream until "end-of-stream" encountered, or write to the opened output stream and optionally flush the buffered output. Reading from an InputStream The abstract superclass InputStream declares an abstract method read to read one data-byte from the input source: Flushing the OutputStream In options, the OutputStream provides a flush method to flush the remaining bytes from the output buffer. For example, the following codes chain a FileInputStream to a BufferedInputStreamand finally, a DataInputStream: Copying a file byte-by-byte without Buffering. For example, the above example can be re-written in a much neater manner as follow: Native2ascii a file options a Programmer-Managed Buffer. Copying a file with Buffered Streams. To use DataInputStream for formatted input, you can chain up the input streams as follows: You can choose the character set in the InputStreamReader 's constructor: The commonly-used Charset names input by Java are: Latin-1 " UTF-8 ": Most commonly-used encoding scheme for Unicode " UTFBE ": Big-endian big byte first big-endian is usually the default " UTFLE ": Little-endian little byte first " UTF ": FE FF indicates big-endian, FF FE indicates little-endian. PrintWriter The byte-based java. Object Serialization and Object Streams Data streams DataInputStream and DataOutputStream allow you to read and write primitive data such as intdouble input Stringrather than individual bytes. Object serialization import java. To prevent certain fields from being serialized, mark them using the keyword transient. This could cut down the amount of data traffic. The writeObject method writes out the class of the object, the class signature, and values of non- static and non- transient fields. Warning Message "The serialization class does not declare a static final serialVersionUID field of type long" Advanced This warning message is triggered because your class such as java. You have these options: Simply ignore this warning message. If a serializable class native2ascii not explicitly declare a serialVersionUIDoptions the serialization runtime will calculate a default serialVersionUID value for that class based on various aspects of the class. Add a serialVersionUID Recommendede. Externalizable Interface The Serializable has a sub-interface called Externalizablewhich native2ascii could used if you want to customize the way a class is serialized. Externalizable declares two abstract methods: Reading and writing ZIP files [ PENDING] Example: Delimiter Instead of the default white spaces as the delimiter, you output set the delimiter to a chosen regular expression via these methods: Customized token delimiter import java. Regexe Pattern Matching You can use the following methods to find the next occurrence of the specified pattern using regular expressions: LF [UTF-8] Formatted-Text Printing with printf method JDK 1. The optional width indicates the minimum number of characters to be output. The optional precision restricts the number of characters or number of decimal places for float-point numbers. The mandatory conversion-type-character indicates how the argument should be formatted. The uppercase conversion code e. The Formatter has the following constructors: The format method can be used to write formatted text output: Path A path string could be used to locate a filea directory or a symbolic link. Paths To create a Pathuse the static method get input the helper class java. For example, import java. Files The class Files contains exclusively static methods for file, directory and symlink operations such as create, delete, read, write, copy, move, etc. Do not follow symlinks. For example, to native2ascii the size of a file in JDK 1. Use static method java. Random Access File The Interface SeekableByteChannel supports random access. List the contents of a directory filtered by a glob. Any file character matches itself. You can also write your own codes to filter the entries.
How to File for Bankruptcy Chapter 7 - It's Not Hard
How to File for Bankruptcy Chapter 7 - It's Not Hard
When goats were first introduced to Hawaii by Captain Cook in the late 1700s, they immediately began eating all the local plant life.
Leaving aside the biological and medical arguments, what I have come to realise is that not eating meat has done me the world of good.