import java.util.HashSet; public class JPTQuestion3 { public static void main(String[] args) { HashSet shortSet = new HashSet(); for (short i = 0; i < 100; i++) { shortSet.add(i); shortSet.remove(i - 1); } System.out.println(shortSet.size()); } } 输出:…

public class JPTQuestion2 { public static void main(String[] args) { String s3 = "JournalDev"; int start = 1; char end = 5; System.out.println(start + end); System.out.println(s3.substring(start, end)); } } 注意:这里的end是char类型,可是,输出结果和int型的end没区别.…

What will be the boolean flag value to reach the finally block? public class JPTQuestion4 { public static void main(String[] args) { try { if (flag) { while (true) { } } else { System.exit(1); } } finally { System.out.println("In Finally"); } }…

public class JPTQuestion1 { public static void main(String[] args) { String s1 = "abc"; String s2 = "abc"; System.out.println("s1 == s2 is:" + s1 == s2); } } 输出:false -----------------------坑爹的是:s1 == s2 is:竟然没有输出,控制台就一个false…

https://docs.oracle.com/javase/7/docs/technotes/tools/windows/javac.html\ javac - Java programming language compiler Synopsis Description Options Command Line Argument Files Annotation Processing Searching for Types Programmatic Interface Examples Se…

引用:Java Programming Language Enhancements Java Programming Language Enhancements Enhancements in Java SE 7 Binary Literals - In Java SE 7, the integral types (byte, short, int, and long) can also be expressed using the binary number system. To specif…

import javax.swing.JOptionPanepublic class welcome {public static void main(string[] arg){JOptionPane.showMessageDialog(null,“welcome to java programming!”);} } public class welcome {public static void main(string[] arg){System.out.println("welcome t…

Thing C Java type of language function oriented object oriented basic programming unit function class = ADT portability of source code possible with discipline yes portability of compiled code no, recompile for each architecture yes, bytecode is "wri…

Difference between Vector and Arraylist is the most common  Core Java Interview question you will come across in Collection .  This question is mostly used as a start up question by the Interviewers before testing deep  roots of  the Collection  .Vec…

This appendix contains suggestions to help guide you in performing low-level program design and in writing code.Naturally, these are guidelines and not rules. The idea is to use them as inspirations and to remember that there are occasional situation…

Java局部变量 局部变量声明在方法.构造方法或者语句块中: 局部变量在方法.构造方法.或者语句块被执行的时候创建,当它们执行完成后,变量将会被销毁: 访问修饰符不能用于局部变量: 局部变量只在声明它的方法.构造方法或者语句块中可见: 局部变量是在栈上分配的. 局部变量没有默认值,所以局部变量量被声明后,必须经过初始化,才可以使用. 实例变量 实例变量声明在一个类中,但在方法.构造方法和语句块之外: 当一个对象被实例化之后,每个实例变量的值就跟着确定: 实例变量在对象创建的时候创建,在对象被销毁…

基本语法 编写Java程序时,应注意以下几点: 大小写敏感:Java是大小写敏感的,这就意味着标识符Hello与hello是不同的. 类名:对于所有的类来说,类名的首字母应该大写.如果类名由若干单词组成,那么每个单词的首字母应该大写,例如 MyFirstJavaClass . 方法名:所有的方法名都应该以小写字母开头.如果方法名含有若干单词,则后面的每个单词首字母大写. 源文件名:源文件名必须和类名相同.当保存文件的时候,你应该使用类名作为文件名保存(切记Java是大小写敏感的),文件名的后缀为…

1.使用循环把26个字母按字典顺序存入数组,在不使用另外数组的情况下将其逆序存放,在根据处理后的字符数组创建一个字符串并输出 public static void main(String[] args) { char a[]=new char[26],c; //中间变量c int i; for(i=0;i<a.length-1;i++){ a[i]=(char)('a'+i); } for(i=0;i<13;i++){ c=a[i]; a[i]=a[25-i]; a[25-i]=c; } St…

这个课程的参考视频在youtube. 主要学到的知识点有: Create new project, choose Java Application. one .jar file/ package(.jar name with the same as package), one package can contains mutiple .java files. Comment mutiple lines by using "/* */"; comment one line by usin…

Original web site: http://algs4.cs.princeton.edu/linux/ Part. I [username:~/] [username:~/] mkdir algs4 [username:~/] cd algs4 [username:~/algs4/] mkdir bin [username:~/introcs/] sudo apt-get update [username:~/introcs/] sudo apt--jdk Part. II wget h…

Instead, object references are passed by value! A method cannot modify a parameter of a primitive type. A method can change the state of an object parameter. A method cannot make an object parameter refer to a new object.…

This is a new series of sharing core Java interview question and answer on Finance domain and mostly on big Investment bank.Many of these Java interview questions are asked on JP Morgan, Morgan Stanley, Barclays or Goldman Sachs. Banks mostly asked c…

2016-12-17  21:10:28 吉祥物:Duke(公爵)    Logo:咖啡(爪哇岛盛产咖啡)  An overview of the software development process.          <编程语言吉祥物之Duke>:http://www.cnblogs.com/turingbooks/p/3585919.html <Java Tutorials Learning Paths>:http://docs.oracle.com/javase/tut…

Awesome系列的Java资源整理.awesome-java 就是akullpp发起维护的Java资源列表,内容包括:构建工具.数据库.框架.模板.安全.代码分析.日志.第三方库.书籍.Java 站点等等. 经典的工具与库 (Ancients) In existence since the beginning of time and which will continue being used long after the hype has waned. Apache Ant - Build…

依稀记得自己第一次编译*.java文件,第一次运行*.class文件.但是六七年过去了,现在运行java写的程序更多的是用tomcat这种web容器.最近有个小需求,写一个监控zookeeper集群的报警器,当发现集群中节点发生变化时,发出邮件和短信通知运维人员.如果这么一个功能也写成一个web项目放到tomcat里,就有些杀鸡用牛刀了.于是就写了一个jar项目,用 java -jar 运行.占用资源少不说,部署启动很简单,也不占用访问端口.但也遇到了很多问题,才发现自己对java命令还是一知半…

Introduction To Obejct The progress of abstraction But their primary abstraction still requires you to think in terms of the structure of the computer rather than the structure of the problem youare trying to solve. The alternative to modeling the ma…

Build Tool Tools which handle the buildcycle of an application. Apache Maven - Declarative build and dependency management which favors convention over configuration. It's preferable to Apache Ant which uses a rather procedural approach and can be di…

Interfaces There are a number of situations in software engineering when it is important for disparate groups of programmers to agree to a "contract" that spells out how their software interacts. Each group should be able to write their code wit…

It’s been a year since I revealed the best languages to learn in 2013. Once again, I’ve examined the data produced by Jobs Tractor who analyzed more than 45,000 developer jobs advertised on Twitter during the past twelve months. The results: Java 8,7…

Now, it is time to gather all the major Java 8 features under one reference post for your reading pleasure. Enjoy! Table Of Contents 1. Introduction 2. New Features in Java language 2.1. Lambdas and Functional Interfaces 2.2. Interface Default and St…

[转]http://www.zhihu.com/question/19937886(里面提到的知识点的链接) 1. Java 语言基础 谈到Java 语言基础学习的书籍,大家肯定会推荐Bruce Eckel 的<Thinking in Java>.它是一本写的相当深刻的技术书籍,Java 语言 基础部分基本没有其它任何一本书可以超越它.该书的作者Bruce Eckel 在网络上被称为天才的投机者,作者的<Thinking in C++>在 1995 年曾获SoftwareDevel…

Java虚拟机运行时栈帧结构(周志明书上P237页) 栈帧是什么? 栈帧是一种数据结构,用于虚拟机进行方法的调用和执行. 栈帧是虚拟机栈的栈元素,也就是入栈和出栈的一个单元. 2018.1.2更新(在网上看到一个更好的解释): 栈帧(Frame)是用来存储数据和部分过程结果的数据结构,同时也被用来处理动态链接 (Dynamic Linking).方法返回值和异常分派(Dispatch Exception). 栈帧在什么地方? 内存 -> 运行时数据区 -> 某个线程对应的虚拟机栈 ->…

1. Q: What is HashMap and Map?A: Map is Interface and Hashmap is class that implements that. 2. Q: Difference between HashMap and HashTable?A:HashMap allows null values as key and value whereas Hashtable doesnt allow HashMap is unsynchronized and Has…

作为Java程序员来说,最痛苦的事情莫过于可以选择的范围太广,可以读的书太多,往往容易无所适从.我想就我自己读过的技术书籍中挑选出来一些,按照学习的先后顺序,推荐给大家,特别是那些想不断提高自己技术水平的Java程序员们.此外,大家可以加入457036818交流群,互相分享一下关于JAVA方面的知识.一.Java编程入门类 对于没有Java编程经验的程序员要入门,随便读什么入门书籍都一样,这个阶段需要你快速的掌握Java基础语法和基本用法,宗旨就是“囫囵吞枣不求甚解”,先对Java熟悉起来再说.…

The string is Immutable in Java because String objects are cached in String pool. Since cached String literals are shared between multiple clients there is always a risk, where one client's action would affect all another client. For example, if one…