It 18 Palm Palm 13th day Course Summary

Finish the 13th day of it 18 Palm Java Foundation Course today:

Learning content:

HashMap

HashSet

EntrySet ()

|--getkey ()

|--getvalue ()

KeySet ()

|--get (Key)

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Performance evaluation with or without buffer

The principle of the buffer is to write the characters into an array and then write the files in bulk, avoiding frequent access to the physical files and increasing efficiency.

Row delimiters can be obtained by means of the method in Java.

The system property name is Line.separator.

The row separators for different platforms are different.

windows7:\r\n

MacOS: \ n

--------------------------------

System.getproperty ("Line.separator"); Execute system Property name/

FileWriter: No buffer function,

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itself does not add any functionality to the inherited OutputStreamWriter.

Write () {

Write the data directly to the file.

Sun.nio.cs.StreamEncoder.write (...);

}

BufferedWriter:

----------------------------------

The writer is wrapped, which defines a buffer, which provides writing to a single character, char[], and a string method.

Improve write efficiency.

Hierarchy tree structure: Object-------BufferedWriter

Flushbuffer (): Clears the buffer and writes the buffer data to the destination.

Close () method: Contains Flushbuffer ().

FileReader

-----------------

Inheritance tree: Object--InputStreamReader----FileReader

Read () {

Inputstreamreader.read () {

Sun.nio.cs.StreamDecoder.read ();

}

}

BufferedReader

------------------

Inheritance tree: Object--BufferedReader----LineNumberReader

Read () {

char[] Cbuf = ...;

CBUF[XXX] = c;

Fill ();

return C;

}

Avoid frequent access to physical files.

byte[] bytes = new byte[1023][1024][1024];

byte[] B2 = bytes;

.

.

.

.

bytes = NULL;

Flush ()//cleanup

Refresh ()//refreshing

Clear ()//clear

OutputStream: Output stream

------------------------

Metadata: Metadata that describes the data.

-----------------------------------

Problems encountered:

The wide range of IO streams requires familiarity with

Questions that need help

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It 18 Palm Palm 13th day Course Summary