#Java_Interview_Question :
6) What gives Java its 'write once and run anywhere' nature?
The bytecode. Java is compiled to be a byte code which is the intermediate language between source code and machine code. This byte code is not platform specific and hence can be fed to any platform.
@javaCode☕️
6) What gives Java its 'write once and run anywhere' nature?
The bytecode. Java is compiled to be a byte code which is the intermediate language between source code and machine code. This byte code is not platform specific and hence can be fed to any platform.
@javaCode☕️
#Refactoring
Lesson 3:
Long Method
📌Signs and Symptoms📌
A method contains too many lines of code. Generally, any method longer than ten lines should make you start asking questions.
📌Reasons for the Problem📌
Like the Hotel California, something is always being added to a method but nothing is ever taken out. Since it is easier to write code than to read it, this "smell" remains unnoticed until the method turns into an ugly, oversized beast.
Mentally, it is often harder to create a new method than to add to an existing one: "But it's just two lines, there's no use in creating a whole method just for that..." Which means that another line is added and then yet another, giving birth to a tangle of spaghetti code.
@javaCode☕️
Lesson 3:
Long Method
📌Signs and Symptoms📌
A method contains too many lines of code. Generally, any method longer than ten lines should make you start asking questions.
📌Reasons for the Problem📌
Like the Hotel California, something is always being added to a method but nothing is ever taken out. Since it is easier to write code than to read it, this "smell" remains unnoticed until the method turns into an ugly, oversized beast.
Mentally, it is often harder to create a new method than to add to an existing one: "But it's just two lines, there's no use in creating a whole method just for that..." Which means that another line is added and then yet another, giving birth to a tangle of spaghetti code.
@javaCode☕️
☕️JAVA Language Community
Treatment for Long Method @javaCode☕️
📌Treatment📌
As a rule of thumb, if you feel the need to comment on something inside a method, you should take this code and put it in a new method. Even a single line can and should be split off into a separate method, if it requires explanations. And if the method has a descriptive name, nobody will need to look at the code to see what it does.
1. To reduce the length of a method body, use Extract Method.
2. If local variables and parameters interfere with extracting a method, use Replace Temp with Query, Introduce Parameter Object or Preserve Whole Object.
3. If none of the previous recipes help, try moving the entire method to a separate object via Replace Method with Method Object.
4. Conditional operators and loops are a good clue that code can be moved to a separate method. For conditionals, use Decompose Conditional. If loops are in the way, try Extract Method.
@javaCode☕️
As a rule of thumb, if you feel the need to comment on something inside a method, you should take this code and put it in a new method. Even a single line can and should be split off into a separate method, if it requires explanations. And if the method has a descriptive name, nobody will need to look at the code to see what it does.
1. To reduce the length of a method body, use Extract Method.
2. If local variables and parameters interfere with extracting a method, use Replace Temp with Query, Introduce Parameter Object or Preserve Whole Object.
3. If none of the previous recipes help, try moving the entire method to a separate object via Replace Method with Method Object.
4. Conditional operators and loops are a good clue that code can be moved to a separate method. For conditionals, use Decompose Conditional. If loops are in the way, try Extract Method.
@javaCode☕️
#Java_Interview_Question
7) What is classloader?
The classloader is a subsystem of JVM that is used to load classes and interfaces.There are many types of classloaders e.g. Bootstrap classloader, Extension classloader, System classloader, Plugin classloader etc.
@javaCode☕️
7) What is classloader?
The classloader is a subsystem of JVM that is used to load classes and interfaces.There are many types of classloaders e.g. Bootstrap classloader, Extension classloader, System classloader, Plugin classloader etc.
@javaCode☕️
#Java_Interview_Question
8) Is Empty .java file name a valid source file name?
Yes, save your java file by .java only, compile it by javac .java and run by java yourclassname Let's take a simple example:
//save by .java only
class A{
public static void main(String args[]){
System.out.println("Hello java");
}
}
//compile by javac .java
//run by java A
compile it by javac .java
run it by java A
@javaCode☕️
8) Is Empty .java file name a valid source file name?
Yes, save your java file by .java only, compile it by javac .java and run by java yourclassname Let's take a simple example:
//save by .java only
class A{
public static void main(String args[]){
System.out.println("Hello java");
}
}
//compile by javac .java
//run by java A
compile it by javac .java
run it by java A
@javaCode☕️
#Java_Interview_Question
10) If I don't provide any arguments on the command line, then the String array of Main method will be empty or null?
It is empty. But not null.
@javaCode☕️
10) If I don't provide any arguments on the command line, then the String array of Main method will be empty or null?
It is empty. But not null.
@javaCode☕️
#Design_Patterns
Design Patterns:
In software engineering, a design pattern is a general repeatable solution to a commonly occurring problem in software design. A design pattern isn't a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.
@javaCode☕️
Design Patterns:
In software engineering, a design pattern is a general repeatable solution to a commonly occurring problem in software design. A design pattern isn't a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that can be used in many different situations.
@javaCode☕️
#Design_Patterns
Uses of Design Patterns
Design patterns can speed up the development process by providing tested, proven development paradigms. Effective software design requires considering issues that may not become visible until later in the implementation. Reusing design patterns helps to prevent subtle issues that can cause major problems and improves code readability for coders and architects familiar with the patterns.
Often, people only understand how to apply certain software design techniques to certain problems. These techniques are difficult to apply to a broader range of problems. Design patterns provide general solutions, documented in a format that doesn't require specifics tied to a particular problem.
In addition, patterns allow developers to communicate using well-known, well understood names for software interactions. Common design patterns can be improved over time, making them more robust than ad-hoc designs.
@javaCode☕️
Uses of Design Patterns
Design patterns can speed up the development process by providing tested, proven development paradigms. Effective software design requires considering issues that may not become visible until later in the implementation. Reusing design patterns helps to prevent subtle issues that can cause major problems and improves code readability for coders and architects familiar with the patterns.
Often, people only understand how to apply certain software design techniques to certain problems. These techniques are difficult to apply to a broader range of problems. Design patterns provide general solutions, documented in a format that doesn't require specifics tied to a particular problem.
In addition, patterns allow developers to communicate using well-known, well understood names for software interactions. Common design patterns can be improved over time, making them more robust than ad-hoc designs.
@javaCode☕️
#Java_Interview_Question
11) What if I write static public void instead of public static void?
Program compiles and runs properly.
@javaCode☕️
11) What if I write static public void instead of public static void?
Program compiles and runs properly.
@javaCode☕️
#Java_Interview_Question
12) What is the default value of the local variables?
The local variables are not initialized to any default value, neither primitives nor object references.
@javaCode☕️
12) What is the default value of the local variables?
The local variables are not initialized to any default value, neither primitives nor object references.
@javaCode☕️
#Java_Interview_Question
13) What is difference between object oriented programming language and object based programming language?
Object based programming languages follow all the features of OOPs except Inheritance. Examples of object based programming languages are JavaScript, VBScript etc.
@javaCode☕️
13) What is difference between object oriented programming language and object based programming language?
Object based programming languages follow all the features of OOPs except Inheritance. Examples of object based programming languages are JavaScript, VBScript etc.
@javaCode☕️
#Java_Interview_Question
14) What will be the initial value of an object reference which is defined as an instance variable?
The object references are all initialized to null in Java.
@javaCode☕️
14) What will be the initial value of an object reference which is defined as an instance variable?
The object references are all initialized to null in Java.
@javaCode☕️
#Design_Patterns
Creational design patterns
These design patterns are all about class instantiation. This pattern can be further divided into class-creation patterns and object-creational patterns. While class-creation patterns use inheritance effectively in the instantiation process, object-creation patterns use delegation effectively to get the job done.
@javaCode☕️
Creational design patterns
These design patterns are all about class instantiation. This pattern can be further divided into class-creation patterns and object-creational patterns. While class-creation patterns use inheritance effectively in the instantiation process, object-creation patterns use delegation effectively to get the job done.
@javaCode☕️
#Design_Patterns
🔴Creational design patterns🔴
✅Abstract Factory
Creates an instance of several families of classes
✅Builder
Separates object construction from its representation
✅Factory Method
Creates an instance of several derived classes
✅Object Pool
Avoid expensive acquisition and release of resources by recycling objects that are no longer in use
✅Prototype
A fully initialized instance to be copied or cloned
✅Singleton
A class of which only a single instance can exist
@javaCode☕️
🔴Creational design patterns🔴
✅Abstract Factory
Creates an instance of several families of classes
✅Builder
Separates object construction from its representation
✅Factory Method
Creates an instance of several derived classes
✅Object Pool
Avoid expensive acquisition and release of resources by recycling objects that are no longer in use
✅Prototype
A fully initialized instance to be copied or cloned
✅Singleton
A class of which only a single instance can exist
@javaCode☕️
#Java_Interview_Question
15) What is constructor?
Constructor is just like a method that is used to initialize the state of an object. It is invoked at the time of object creation.
@javaCode☕️
15) What is constructor?
Constructor is just like a method that is used to initialize the state of an object. It is invoked at the time of object creation.
@javaCode☕️
☕️JAVA Language Community
#Java_Interview_Question 15) What is constructor? Constructor is just like a method that is used to initialize the state of an object. It is invoked at the time of object creation. @javaCode☕️
More details:
👉Constructor in Java
Constructor in java is a special type of method that is used to initialize the object.
Java constructor is invoked at the time of object creation. It constructs the values i.e. provides data for the object that is why it is known as constructor.
👉Rules for creating java constructor
There are basically two rules defined for the constructor.
Constructor name must be same as its class name
Constructor must have no explicit return type
Types of java constructors
👉There are two types of constructors:
1️⃣Default constructor (no-arg constructor)
A constructor that have no parameter is known as default constructor.
2️⃣Parameterized constructor
A constructor that have parameters is known as parameterized constructor.
Why use parameterized constructor?
Parameterized constructor is used to provide different values to the distinct objects.
@javaCode☕️
👉Constructor in Java
Constructor in java is a special type of method that is used to initialize the object.
Java constructor is invoked at the time of object creation. It constructs the values i.e. provides data for the object that is why it is known as constructor.
👉Rules for creating java constructor
There are basically two rules defined for the constructor.
Constructor name must be same as its class name
Constructor must have no explicit return type
Types of java constructors
👉There are two types of constructors:
1️⃣Default constructor (no-arg constructor)
A constructor that have no parameter is known as default constructor.
2️⃣Parameterized constructor
A constructor that have parameters is known as parameterized constructor.
Why use parameterized constructor?
Parameterized constructor is used to provide different values to the distinct objects.
@javaCode☕️