What is the most important feature of Java?Java is a platform independent language.What do you mean by platform independence?Platform independence means that we can write and compile the java

Can a class be declared as protected?A class can’t be declared as protected. Only methods can be declared as protected.What is the access scope of a protected method?A protected method can be

Can an abstract class be defined without any abstract methods?Yes, it’s possible. This is basically to avoid instance creation of the class.Class C implements Interface I containing method m1 an

What is a local, member and a class variable?Variables declared within a method are “local” variables.Variables declared within the class i.e not within any methods are “member” variables (global

1. Which object oriented concept is achieved by using overloading and overriding?Polumorphism2. Why does Java not support operator overloading?Operator overloading makes the code vert difficult

Does a class inherit the constructors of its superclass?A class does not inherit constrcutors from any of its superclass.Name the eight primitive Java Types.The eight primitive types are byte,

What restrictions are placed on the location of a package statement within a source code file?A package statement must appear as the first line in a source code file (excluding blank lines and comme

package com.citi.hnw.mainframe;import java.sql.Connection;import java.sql.DriverManager;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.Ar

When an application contains just one version of a method, you can call the method using a parameter of the correct data type or one that can be promoted to the correct data type. For example, you can

When you instantiate an object from a class, memory is reserved for each instance field in the class. For example, if a class contains 20 data fields, when you create one object from that class, enoug

虚引用(Phantom References)并不会决定对象的生命周期。如果一个对象仅持有虚引用，那么它就和没有任何引用一样，在任何时候都可能被垃圾回收器回收。虚引用主要用来跟踪对象被垃圾回收器回收的活动。虚引用与软引用和弱引用的一个区别在于：虚引用必须和引用队列(Reference Queue)联合使用。当垃圾回收器准备回收一个对象时，如果发现它还有虚引用，就会在回收对象的内存之前，把这个虚

弱引用(Weak References)只具有弱引用的对象拥有更短暂的生命周期。在垃圾回收器线程扫描它所管辖的内存区域的过程中，一旦发现了只具有弱引用的对象，不管当前内存空间足够与否，一概回收。不过，由于垃圾回收期是一个优先级很低的线程，所以不一定能执行。弱引用可以和一个引用队列(Reference Queue)联合使用，如果弱引用所引用的对象被垃圾回收，JVM就会把这个弱引用加入到与之关联的

In Java, you can create a class within another class and store them together such classes are nested classes. The containing class is the top-level class. There are four types of nested classes:Stat

1. 选择排序选择排序的基本思想是遍历数组的过程中，以i代表当前需要排序的序号，则需要在剩余的[i..n-1]中找出其中的最小值，然后将找到的最小值与i指向的值进行交换。因为每一次确定元素的过程中都会有一个选择很大值的子流程，所以称之为选择排序。比如[38, 17, 16, 16, 7, 31, 39, 32, 2, 11]i = 0:  [2 , 17, 16, 16, 7, 31,

Java strings are objects designed to represent a sequence of characters. Because character strings are commonly used in programs, Java supports the ability to declare String constants and perform conc

How to convert char array to String in JavaUse copyValueof() method to copy value from array to String objectpublic class CharArrayToString { public static void main(String a[]){ char ch[] = {

List of objects that implement this interface can be sorted automatically by sort method of the list interface. This interface has compareTo() method that is used by the sort() method of the list.In

try {   String jdbcURL ="jdbc:oracle:thin:@fitwsswdb1.nam.nsroot.net:1522:RVDBP1";   Properties props = new Properties();   props.put("user", "rvuser");      props.put("password", "user123");

强引用(Strong references)是使用最普遍的引用。如果一个对象具有强引用，那么垃圾回收器绝不会回收它，即便内存不足JVM也会选择抛出OutOfMemoryErro，强行终止程序也不会随意回收具有强引用的对象来解决内存不足的问题。String s = new String(“opps”);这种形式的引用成为强引用,它有以下特点:强引用可以直接访问目标对象.强引用所指向的对象

软引用(soft references)只要垃圾回收器没有回收它，该对象就可以被程序使用。软引用可用来实现内存敏感的高速缓存。软引用可以和一个引用队列(Reference Queue)联合使用，如果软引用所引用的对象被垃圾回收器回收，JVM就会把这个软引用加入到与之关联的引用队列中。import java.lang.ref.SoftReference;import java.util.Ar

public String(char value[], int offset, int count) {if (offset   throw new StringIndexOutOfBoundsException(offset);   }  if (count   throw new StringIndexOutOfBoundsException(count);  }

The example compares two strings by using str compareTo(string), str compareTolgnoreCase(String) and str compareTo(object string) methods of string class and returns the ascii difference of first odd

Overriding toString(), hashCode() and equals() MethodsOverridde toString() when you want to be able to read something meaningful about the objects of your class. Code can call toString() on your obj

In object-oriented terminology, a class is a term that describes a group or collection of objects with common properties. A class definition describes what attribute its objects will have and what tho

Final如果final修饰的是一个基本类型，就表示这个变量被赋予的值是不可变的，即它是个常量；如果final修饰的是一个对象，就表示这个变量被赋予的引用是不可变的。如果一个变量或方法参数被final修饰，就表示它只能被赋值以此，但是jvm为变量设定的默认值不记作一次赋值。Final变量无论是否静态的都必须在定义时即赋值，不允许后面再赋值，会抛错。public final int A=

Run Configurations里需要在JVM中配置加载信息，这里不支持空格，-DCONFIG_PATH=C:\logs\ -DENV=uat需要将配置文件导入到build path中，在文件夹处右键add to build path/classpath。

1、卓越的程序员Fred George先生说：“不编程的架构师的职业生涯是短暂的”。他说这句话的背景主要是针对有些架构师的设计与实现有断层的问题而言的，因为如果架构师不去实践，只是想当然的认为“没问题，这个想法能实现”，那么对于项目的落实而言是个很大的隐患。支付宝架构师冯大辉也表示过，架构师是一个比较“虚”的岗位，主要的问题都在“落地”的过程中。2、抽象思维很多优秀的架构师们都一致的表

物件容器(container) Collection接口分装了不同类型的容器，可以看上图所示。物件容器可以帮你持有对象。在Java中分作两大类： Collection和Map。前者可持有各自独立的物件，后者持有承兑的key-value物件。注意所有的核心collection接口是通用的，如何申明一个Collection接口：Iterator iterator=collect

三点建议：不要使用System.out.println作为调试工具 把所有涉及到的组件日志级别激活并使用 使用日志分析器来读取日志 1.条件断点如果你不知道如何添加断点，只需点击左边面板（行号前面）断点即被创建。在调试界面中，“断点”视图会把所有被创建的断点列出来。我们可以给它加一个布尔条件，也就是说，该断点会被激活并且如果布尔条件为真，就会执行该断点，否则将会跳过往下执行。

Data StructureA literal numeric constant contains digits and an optional sign that indicates whether the constant is positive or negative. Floating-point constants also contain a decimal point. In t

How many static initializers can you have?As many as you want, but the static initializers and class variable initializers are exected in textual order and may not refer to class variables declared

有一个已经有序的数据序列，要求在这个已经牌号的数据序列中插入一个数，但要求插入后此数据序列仍然有序，插入排序法插入排序的基本操作就是将一个数据插入到已经排好序的有序数据中，从而得到一个新的，个数加一的有序数据，算法适用于少量数据的排序，时间复杂度为O(n^2)。它是稳定的排序方法，插入算法把要排序的数组分成两部分：第一部分包含了这个数组的所有元素，但将最后一个元素除外，而第二部分就只包含这一个元素

public static void main(String[] args){      //字符串有整型的相互转换         String str=String.valueOf(123);         int i=Integer.parseInt(str);         System.out.println(i);         //向文件末尾添加内容

public static void main(String[] args){      //字符串有整型的相互转换         String str=String.valueOf(123);         int i=Integer.parseInt(str);         System.out.println(i);         //向文件末尾添加内容

As an object, a String variable name is not a simple data type—it is a reference; that is, a variable that holds a memory address. Therefore, when you compare two Strings using the == operator; you ar

String is a class, and created String is a class object. A string variable name is a reference; that is , a String variable name refers to a location in memory, rather than to a particular value. Bu

In java, the value of a String is fixed after the String is created; Strings are immutable, or unchangeable. When you write someString=”Hello”; and follow it with someString=”Goodbye”; you have nerith

单例模式(Singleton)

定义泛型接口和类

An array is a named list of data items that all have the same type. You declare an array variable in the same way you declare any simple variable, but you insert a pair of square rackets after the typ