Decoration mode (old love) and decoration Mode

Decoration mode (old love) and decoration Mode

| -- What is the decoration mode.

Decoration mode: whether it is you or you. Please use the classic words of Lao Cui ).

It appears from inheritance, first inherited, and then decorated.
Recall inheritance
Benefits: Improves reusability and enables reuse. Later extensions can be used through method rewriting.
Disadvantage: because of the inheritance relationship between classes, their relationships are enhanced, and their coupling is high. Not in line with java's purpose: low coupling and high cohesion.

Comparison:
A: There is a Witer system.
| -- TxtWrite
| -- Mp3Write
| -- DIDWrite
The above is a common subclass implementation. The caller thinks the execution is too slow and needs to enhance the three (efficient | buffering ). Modify as follows:
Class myBuffereWrite exetends Write {
// Receiving subclass: Fu f = new Zi ();
Private Write ziWrite;


Public BuffereWrite (Write ziWrite)
{
This. ziWrite = ziWrite;
}
Public void writeLine (String line)
{
// Use ziWrite for cosmetic processing, and save a row of data to write.
}
Public void close ()
{
ZiWrite. clese (); // polymorphism (called or subclass )!
}
Public void flash (){
ZiWrite. flash (); // polymorphism (called or subclass )!
}
... // Rewrite the abstract method of Write. In myBuffereWrite, the call in the method is to transfer ziWrite. Just calling it
I had some surgery on it before.
}

| -- Summary
1: for example, if you use the efficient Write function, you can create myBuffereWrite and pass your efficient objects, such as FileWrite ();
2: The decoration mode reflects the enhancement (High Cohesion) of an object (function), and then the tightness is relatively weak (low coupling ).
3: JDK uses a lot of decorations, such as BufferedWriter (Writer out), PrintStream (OutputStream out), and ObjectInputStream (InputStream in.

| -- Sample Code

Simulate buffererereader decoration class

Package com. decoration; import java. io. IOException; import java. io. reader;/*** @ author hubiao * simulate buffererereader decoration class ** analysis: simulate a class, that is, to customize a class and implement its unique method: ReadLine (); * 1: simulation: Special Method * 2: What do you have: According to the decorative characteristics, a custom class inherits an abstract class, because the underlying layer of BuffereReader's readLine inherits from Reader. * What we need to do is inherit Reader and write a ReadLine method that is the same as BuffereReader. */Public class MyBuffere extends Reader {/* Reader is the parent class of an abstract class and implements all the classes that require efficiency. Is its subclass. */Private Reader reader = null; public MyBuffere (Reader reader) {this. reader = reader;} public int read (char [] cbuf, int off, int len) throws IOException {return reader. read (cbuf, off, len);} public String readLine () throws IOException {/*** 1: here you need to think about it. Use * A: read (char [] cbuf, int off, int len); read a buffer at a time * B: read (); // read a string at a time * 2: Analysis * What is the purpose of simulating readLine? It is not an efficient method for reading a row at a time in readerLine of BufferedReader. * It is not appropriate to use method A because it reads the length defined by A char capacity at A time, and the encapsulated code is difficult to know how long each row of Data Text the caller wants to read. * The advantage of using the B method is to read one character at a time. When \ r \ n is returned, it indicates that the reading of one row is complete, how can we store each character in a row of data? * It's terrible to use String, because we know that String is a constant pool in java. 1. The value assignment is unchangeable. Therefore, the highly efficient StringBuilder * concatenates each character into the StringBuffer and returns it to the caller. * /// Single-character container StringBuffer buffer = new StringBuffer (); // each character int read = 0; while (read = reader. read ())! =-1) {char chr = (char) read; if (chr = '\ R') continue; if (chr =' \ n') return buffer. toString (); elsebuffer. append (chr);} // prevents the last row from being read, and \ r \ n is not displayed. Then, check whether there is a value in the buffer zone? If yes, return again. If (buffer. length ()> 0) return buffer. toString (); elsereturn null;} public void close () throws IOException {reader. close ();}}

Simulate LineNumberReader

/*** @ Author hubiao * simulates LineNumberReader *. Similarly, the simulation is to define a class. The special method provided by the simulation requirement is to obtain each row and then read each row. */Public class MyLineNumberReader extends Reader {/* receives the passed subclass object, Fu f = new Zi (); // polymorphism */private Reader reader; private int lineNumber; // The row number is public MyLineNumberReader (Reader reader) {this. reader = reader;} public int read (char [] cbuf, int off, int len) throws IOException {return reader. read (cbuf, off, len);} public String readLine () throws IOException {// single character container StringBuffer buffer = new StringBuffer (); // each character int Read = 0; while (read = reader. read ())! =-1) //-1 indicates reading to the end of the stream! {Char chr = (char) read; if (chr = '\ R') continue; if (chr =' \ n') {lineNumber ++; return buffer. toString ();} elsebuffer. append (chr);} // prevents the last row from being read, and \ r \ n is not displayed. Then, check whether there is a value in the buffer zone? If yes, return again. If (buffer. length ()> 0) {lineNumber ++; return buffer. toString ();} elsereturn null;} public void close () throws IOException {reader. close ();} public int getLineNumber () {return lineNumber;} public void setLineNumber (int lineNumber) {this. lineNumber = lineNumber ;}}

Java: helper for the modifier Mode

No. If the others remain unchanged, you can change the implementation to inheritance. The reason why the decoration class implements the same parent interface of the decorated class is to get the same functions, and inherit the class directly. Other codes are written according to the decoration class. It is not a method to override the parent class.

Different java decoration modes and inheritance

Create a new decoration class and declare a method that requires extended functions,
Call the extended functions in this method, and then call the basic functions of the decorated class,
To extend the basic functions of the decoration class.

For details, see:
Jiangnanlove.iteye.com/blog/914120

Hope to help you.