stack | 易学教程

java inheritance versus composition (implementing a stack)

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I am trying to implement a Stack in java (using the list interface: Interface List ). I want to implement it two different ways: using composition and inheritance. For inheritance, so far I have: import java.util.Collection; import java.util.Iterator; import java.util.List; import java.util.ListIterator; public class StackInheritance implements List { //implement list methods } For composition, I have: import java.util.List; public abstract class StackComposition implements List { // implement some standard methods } public class StackViaList extends StackComposition { // implement methods

html stack order

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Consider the following code: <!DOCTYPE html> <html lang="en"> <head> <title>HTML</title> <meta charset="utf-8" /> <style type="text/css"> h1 { font-size: 2em; font-family: Verdana; font-weight: bold; } p { border: 3px solid blue; margin-top: -50px; background-color: green; color: white; } </style> </head> <body> <h1>QUESTION</h1> <p>The header text in the preceding h1 element is behind this paragraph's text (as expected), but on top of this paragraph's background and border (not expected). </p> </body> </html> See the example here: http://jsfiddle.net/ZKHc9/ Why isn't the paragraph's

How java works in android through memory object heap allocation

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I am new to Android but experienced in Java . In Java when we do this: MyClass myObj = new MyClass(); It clearly does the following: Inserts the memory pointer myObj upto the stack Allocates a new space for object of type MyClass in the heap Appoints this new space's reference to myObj But I am a little bit confused about the following questions: But in Android , does this work in the same way? Does Android have full stack and heap memories? Does Android have Java Virtual Machine (JVM) for my Java app ( Android app) to work on? Thanks a lot! Android re-implemented the Java Virtual Machine with

Is there a drop-in replacement for Java Stack that is not synchronized?

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问题 I have a large codebase (written by me) that uses the Stack data structure. This was used for convenience and I am using it as Stack sometimes or Vector/List some other times. After a performance review however it was decided that we do not want to pay extra for the synchronization safety. I need now to replace this structure with a non-synchronized one (and it is mentioned a lot of times in the code). I was happy to discover that Apache collections includes an ArrayStack which is exactly

How to implement a dequeue using two stacks

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Dequeue - Doubly ended queue: en-queue and de-queue possible from both ends. How to define ADT operations for dequeue using 2 stacks. Implementation should also take into consideration the performance. the simplest solution would be to use one stack as the head of the queue, and one as the tail. The enqueue operations would just be a push to the respective stack, and the dequeue operations would just be a pop on the respective stack. However, if the stack you want to dequeue from is empty, you'd have to pop each element from the other stack and push it back to the stack you want to dequeue

Does there exist Kernel stack for each process ?

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问题 Does there exist a Kernel stack and a user-space stack for each user space process? If both stacks exist, there should be 2 stack pointers for each user space process right? 回答1: In Linux, each task (userspace or kernel thread) has a kernel stack of either 8kb or 4kb, depending on kernel configuration. There are indeed separate stack pointers, however, only one is present in the CPU at any given time; if userspace code is running, the kernel stack pointer to be used on exceptions or

Stack in Java, problem with “contains”

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I'm using stack in my program but I have a problem when program is trying to check what element contains in stack. I'm using array of integer in Stack. Short example is: Stack<int[]> myStack = new Stack<int[]>(); myStack.push(new int[]{1,2}); myStack.push(new int[]{1,3}); myStack.push(new int[]{1,4}); if (myStack.contains(new int[]{1,3})) { System.out.println("YES"); } else { System.out.println("NO"); } Now it was printed "NO". How could I do to get "YES" ? I know that the problem is that I'm not using same object but in the reality my program is much larger and I can't to use this int[]

Multiple threads calling the same function

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问题 Suppose we have multiple threads all calling the same function: def foo # do stuff ... end 100.times do |i| Thread.new do foo end end If two or more threads are currently inside of foo , do they each share the same local variables within foo ? This relates to my second question. Do threads have individual stack frames, or do they share stack frames within a single process? Specifically, when multiple threads each invoke foo and before foo returns, are there multiple copies of foo on the stack

Bring rasters to same extent by filling with NA - in R

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I have several cropped rasters with different geometry/outlines. Specifically spatial yield maps from several years of the same field, but the extent varies - the measurements were not always overall the whole field, but in some years only part of it. I want to calculate a mean value of those maps and combine them into one mean-value-raster. That does mean however, that not for every pixel in let's say 5 layers/rasters there is a value. I could accept these missing values to be NA, so the final mean value would only be calculated by let's say 3 rasters for parts of the field, where the maps

Does C need a stack and a heap in order to run?

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问题 People talk about what the stack and heap are and the differences between them. But I am curious to know that if a CPU does not support stack and heap structure, then can C run properly without a stack and a heap? 回答1: No, it does not. Let's cover the heap first, that's easy. An implementation that does not provide a heap of any sort just needs to return NULL whenever you try to call malloc (or any other memory allocation function). That's perfectly acceptable behaviour according to the