clone - In Java, what is a shallow copy? -

-

java.util.Calendar.clone () returns "a new calendar with the same properties" and returns "returns" This shallow copy of this calendar ".

This is not a shallow copy as the answer has been tagged to the question language-agnostic, Java language does not follow the agnostic definition As I stepped through the code, I see that the structure and the elements are copied to this new object, the cave

What is a shallow copy in Java?

Is it different from a Java deep copy (if it exists)?

A shallow copy just copies the values ​​of references given in the class, copies a deep copy values ​​given: < / P> 

  class Foo {private bar myBar; ... public foo shallow (copyright) (Foo newFoo = new Foo ()); NewFoo.myBar = myBar; New Return;} Public Foo deepCopy () {Foo newFoo = new Foo (); NewFoo.myBar = myBar.clone (); // or newer bar (mayabara) or merchandise dip copy or ... take new afoo; }} Foo Miefu = New Foo (); Foo SFu = MaiFhu.Salopi (); Foo dfu = myFoo.deepCopy (); MyFoo.myBar == sFoo.myBar = & gt; True myFoo.myBar.equals (sFoo.myBar) = & gt; True myFoo.myBar == dFoo.myBar = & gt; ** False ** myFoo.myBar.equals (dFoo.myBar) = & gt; True is the shallow copy of the same reference ( == ) in this case and deep copy has only one parallel reference ( .equals ()). ) ). 
 
 If any change is done for the value of the shallow copy reference, then copy reflects that change because it shares the same context. If there is a deeper change in the value of the copy reference, then the copy does not reflect that change because it does not share the same context. 
 
 C-ism 
 
  Int A = 10; // init int & amp; B = A; // shallow - copies reference c = a; // deep - copies VALUE ++ a;  
 
 Result: 
 
  a is 11 * b 11c 10

Comments

Post a Comment

Popular posts from this blog

c# - ListView onScroll event -

-
I am programming a simple C # application, and I need a Scallow event on the list view. So I inherited the original ListView class created in ListviewEx witch. I found out how to locate the scroll message from WinAPI and I modified the WndProc method. Now I have this WndProc: protected override zero WndProc (Ref message message) {base.WndProc (Ref I); If (m.msg == WM_VSCROLL) {onScroll (This, New EventArgs ()); }} But the problem is, I do not know how to know about scrolling information. This data should be in wParam, but there is a LOWORD macro ++ like in C in C # and I switch to find the criteria like SB_ below, SB_ENDSCROLL, SB_PAGEUP etc. there any way Need to change the LOWORD macro from C #? Or any other way to find the necessary parameters about scrolling? You can define the WParam constants as the following: Private const int WM_HSCROLL = 0x114; Private Constant WM_VSCROLL = 0x115; Private contact int SBHOZZ = 0; Private Consultant SB_VERT = 1; Private Con...
Read more

PHP - get image from byte array -

-
I am trying to create a back-end for my mobile application. I am sending the content of an image in the body of the HTTP request (output stream) as a byte array, I want to read this stream of bytes in PHP scripts and take back an image. Can anyone tell me how can I do this? Thank you. You can obtain the request body $ body = Reading from file_get_contents ('php: // input'); What you do with that data Depending on you, you can write the data in a file as you mentioned that this is image data, you can drop the data into the object can do. Another option is to use and load the image.
Read more

Linux Terminal Problem with Non-Canonical Terminal I/O app -

-
I have a small app written in C to run on Linux. Part of the app accepts user-input from keyboard , And it uses non-canonical terminal mode so that it can respond to each keystroke. The section of the code that accepts input is a simple task that is called repeatedly in the loop: char get_input () {char C = 0; Int res = reading (input_tamille, & amp; c, 1); If (RSS == 0) 0 returns; If (res == -1) {/ * snip error handling * /} return c; } It reads a letter from the terminal if there is no input within a given time limit, (c_cc [VTIME] value in the vocabulary structure), read () 0 And get_input () is called again It all works very well, I have recently discovered that if you run this app in a terminal window, and then the app Close the terminal window without ending, the app will not exit Received, but CPU intensive launches into an infinite loop, where the read () returns 0 without waiting continued. So how can I get out of the apple if it runs from the terminal win...
Read more