Java IO Stream, collection class part small Knowledge point summary

In Java, the following three classes are often used to process data streams, and the following describes the differences between the three classes and their usage.

• InputStream: is a superclass of all byte input streams, generally using its subclasses: FileInputStream, etc., it can output byte stream;
• InputStreamReader: It is a bridge between the byte stream and the character stream, can output the character stream as a character stream, and can specify the character set for the byte stream, and can output one of the characters;
• BufferedReader: Provides a common buffered text read, ReadLine reads a line of text, reads text from the character input stream, buffers individual characters, and provides efficient reading of characters, arrays, and rows.

Example:

Convert bytes to character stream
InputStreamReader reader = new InputStreamReader (new FileInputStream (targetfile));
Provides universal buffering of text reads
BufferedReader br = new BufferedReader (reader);

Iterators (Iterator)

• (1) Use method iterator () requires the container to return a iterator. The first time you call Iterator's next () method, it returns the first element of a sequence. Note: The iterator () method is an Java.lang.Iterable interface that is inherited by collection.

• (2) Use Next () to get the next element in the sequence.

• (3) Use Hasnext () to check if there are elements in the sequence.

• (4) use remove () to delete the newly returned element of the iterator.

Example:

Iterators for while Loops
Iterator iter = L.iterator ();
while (Iter.hasnext ()) {
String str = (string) iter.next ();
System.out.println (str);
}

list and Listfiles methods in the file class

• The list () method returns the file names of all files and directories under a directory, and returns a string array
• The Listfiles () method returns the absolute path to all files and directories in a directory, and returns a file array

List of Add () and AddAll () methods

• Result.addall (list); //Add each element in the list to result, result.size () = = List.size ()
• Result.add (list); //Add list as an element to result, then Result.size () is 1

Java IO Stream, collection class part small Knowledge point summary