arraylist | 易学教程

Nested array slicing

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问题 Let's say I have an array of vectors: """ simple line equation """ function getline(a::Array{Float64,1},b::Array{Float64,1}) line = Vector[] for i=0:0.1:1 vector = (1-i)a+(i*b) push!(line, vector) end return line end This function returns an array of vectors containing x-y positions Vector[11] > Float64[2] > Float64[2] > Float64[2] > Float64[2] . . . Now I want to seprate all x and y coordinates of these vectors to plot them with plotyjs. I have already tested some approaches with no success!

How to Check if an ArrayList Contain 2 values?

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问题 is there any way to check if a collection contain a value or more with better performance than looping twice with contains? in other meaning something that would look like this person.contains("Joe" || "Jasha"); 回答1: The implementation of ArrayList.contains() loops through every element and does an equals() test, so calling .contains() twice is inefficient . You could write your own loop that check both at once using a compiled regex Pattern that looks for either name at the same time:

Syncronized sorting between two ArrayLists

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问题 I have two ArrayLists. The first contains a group of words with capitalization and punctuation. The other contains this same group of words, but with the capitalization and punctuation removed. . ArrayList1 ..... ArrayList2 MURDER! ........ murder It's ........... its Hello .......... hello Yes-Man ........ yesman ON ............. on The second array has all the words alphabetized and all the letters in each word alphabetized. It looks something like this: aemnsy demrru ehllo ist no I want to

Syncronized sorting between two ArrayLists

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java.lang.IndexOutOfBoundsException: Index 7, Size:7

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问题 I am creating a program that finds the solutions to the eight queens problem by breadth search. My code so far: import java.util.*; import java.lang.*; import java.io.*; public class EightQueens { public static void main(String[ ] args) { ArrayList<List<Integer>> states = new ArrayList<List<Integer>>(); List<Integer> start=new ArrayList<Integer>(); for (int s=0; s<8; s++) { start.add(0); } states.add(start); List<Integer> a = new ArrayList<Integer>(); List<Integer> b = new ArrayList<Integer>(

arraylist扩容时机java8

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扩容时机:当新插入一个元素，此时超过了最大容量时，就会扩容，在java8中扩容是1.5倍。和map不要搞混哦。可以debug跟踪一下。代码， private void ensureCapacityInternal(int minCapacity) { ensureExplicitCapacity(calculateCapacity(elementData, minCapacity)); } private void ensureExplicitCapacity(int minCapacity) { modCount++; // overflow-conscious code if (minCapacity - elementData.length > 0) grow(minCapacity); } public boolean add(E e) { ensureCapacityInternal(size + 1); // Increments modCount!! elementData[size++] = e; return true; } 来源： CSDN 作者： alin1215 链接： https://blog.csdn.net/alin1215/article/details/103616784

几种简单的负载均衡算法及其Java代码实现

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什么是负载均衡负载均衡，英文名称为Load Balance，指由多台服务器以对称的方式组成一个服务器集合，每台服务器都具有等价的地位，都可以单独对外提供服务而无须其他服务器的辅助。通过某种负载分担技术，将外部发送来的请求均匀分配到对称结构中的某一台服务器上，而接收到请求的服务器独立地回应客户的请求。负载均衡能够平均分配客户请求到服务器阵列，借此提供快速获取重要数据，解决大量并发访问服务问题，这种集群技术可以用最少的投资获得接近于大型主机的性能。负载均衡分为软件负载均衡和硬件负载均衡，前者的代表是阿里章文嵩博士研发的LVS，后者则是均衡服务器比如F5，当然这只是提一下，不是重点。本文讲述的是" 将外部发送来的请求均匀分配到对称结构中的某一台服务器上 "的各种算法，并以Java代码演示每种算法的具体实现，OK，下面进入正题，在进入正题前，先写一个类来模拟Ip列表： 1 public class IpMap 2 { 3 // 待路由的Ip列表，Key代表Ip，Value代表该Ip的权重 4 public static HashMap<String, Integer> serverWeightMap = 5 new HashMap<String, Integer>(); 6 7 static 8 { 9 serverWeightMap.put("192.168.1.100",

Don't use ArrayList!

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问题 People often tell me not to use ArrayList for making my arrays in VB.NET. I would like to hear opinions about that, why shouldn't I? What is the best method for creating and manipulating array contents, dimensions etc? Thanks. 回答1: Use generic lists instead. ArrayList is not typed, meaning that you can have a list with strings, numbers, +++. Rather you should use a generic list like this: Dim list1 As New List(Of String) ' This beeing a list of string The lists-class also allows you to expand

JAXB Marshalling generic list with variable root element name

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问题 So I'm trying to marshal a generic list of objects, but i want each list to have a specific XmlRootElement(name..). The way I'm doing it, I know it's not really possible without writing a specific wrapper class for each type of object and declaring the XmlRootElement. But maybe there's another way...? Consider the following classes: abstract public class Entity { } @XmlAccessorType(XmlAccessType.FIELD) @XmlRootElement(name="user") public class User extends Entity { private String username;

ArrayList automatically adding null items

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问题 Hello everyone. I'm making a vocabulary App, in which I need to create a List<String> (or ArrayList). To do so, I've created the following piece of code (just an example): List<String> tempSOLUTION = new ArrayList<String>(); String temp = "abc123"; tempSOLUTION.add(temp); I've also tried the following: tempSOLUTION.add(new String(temp)); Both of them add the item to the list, but while debugging, I find that it's array has 12 objects, which are the following: [abc123, null, null, null, null,