How Many Keywords in Java List and Explanation

JAVA Keywords Overview

Java keywords are the most important part of the syntax of the language and have the specific objective of providing instruction to the compiler. These keyword words can not be redefined or reused as identifiers, e. g. variable names, class names, and method names. An interesting feature of Java keywords, however, is that they are case sensitive (they are all lower-case, e.g., if is correct, but If is not). Each keyword is already defined to have a specific function; either to define structural specifications, flow control, or layout with respect to data types. There are some keywords whose use is limited to context as well, like the use of extends is limited to inheritance only in class declarations. More than that, the keywords should be entered with normal ASCII characters and not the Unicode variations.

Types of Java keywords

Java keywords may be divided according to their purpose in the language.

Access Modifiers

Access modifiers determine accessibility to classes, methods as well as variables enabling encapsulation and code security.

private: Allows access to a member (field, method, constructor) to the object of its own type.

protected: Only members of the same package can access it, and also subclasses can access them.

public: Allows a member of any other class to take access.

The Modifiers of Class, Method, and variable

These keywords aid in the definition of classes, behaviors and methods of variables.

abstract Causes a class or method to be abstract: a class or method that may not be instantiated directly, and which must be implemented by subclasses in order to supply concrete versions of abstract methods in the class. An abstract method is not compulsory to an abstract class.

class: A definition of a type of object: a class is a blue print to make objects.

default: The default keyword declares a block of code in switch statements or interfaces by default only.

extends: Means that a class is derived by another class or an interface is inherited by another interface, which enables the class to receive properties and methods belonging to the superclass. It also could set an upper limit over a type parameter in Generics.

final: Announces an entity after which it is not able to change or be derived later on. This is the case with classes (not declassable), methods (not overridable) and variables (not reassignable).

implements: Defines that a class implements a single or multiple interfaces, which have abstract methods and they are implemented.

interface: Declares an interface, a special type of class that includes abstract procedure as well as constants.

native: Indicates that the implementation of a method is supplied in some other language, normally through the Java Native Interface (JNI).

new: It creates a new object or an array.

static: Makes a field, method or inner class a class member, i.e. a member of the class, not an instance member.

: Ensures strict floating point calculations so that different platforms will have the same result. Based on this keyword, it is obsolete.

synchronized: Indicates that a method or a block of code may be accessed by only a single thread at given time hence thread-safe accessing.

transient: Indicates that an instance field should not be serialized as part of default object serialization.

volatile: Declares that the value of a field might change asynchronously due to the action of another thread and that changes of values are properly visible to the other threads in main memory.

void: Declares that a method will not leave a value.

Flow Control

The use of these keywords assists in developing control flow constructs that determine how some blocks of code should be executed.

break: Leaves a loop or a switch block.

case: Delimits a block of code in switch statements, and will be called, given that it matches to the stipulated value.

continue: In the current loop negates the remaining iteration and jumps to the next iteration.

do: With the keyword while it is used to make a do-while loop, which executes a group of statements at least once before testing the value of a boolean expression.

else: A keyword combining with if statement to implement a block of code in case the condition with if is false.

for: Generates one or more loop sequencing statements that are a for-loop with initialization, a test (boolean expression), and an incrementation, and iterates a definite number of times, or over sequences.

if: It establishes a conditional code execution that executes a block of code in case a given condition is truthful.

instanceof: The binary operator checks whether an object is a member of a certain class or an interface.

return: Ends the action of a method and may be used to give a value back.

switch: Chooses a block of code, among a wide variety of blocks, to run depending on a matching value.

while: It establishes a loop that will continue to perform a block of statements till a condition is performed.

Package Control

These keywords control the packaging of classes and interfaces in packages.

import: Invoked at the top of a source file to define classes or whole Java packages to be mentioned without a complete mention of their package names.

package: A declaration that defines and identifies a collection of classes and interfaces: packages exist in a hierarchical relationship.

The Data Types which are primitive are:

These keywords determine the datatype of variables, what type of data they can have.

boolean: It holds a true or false.

byte: A 8-bit signed number that can store whole numbers between -128 and 127.

char: a single 16-bit Unicode character.

double: The storage on 64-bit floating-point numbers (1.7e-308 to 1.7e+308).

float: A single-precision floating-point number covering approximations to non-integral numbers between 3.4e-38 and 3.4e38.

Error Handling

These are exception handling keywords and they allow error-proofed and bug-free code.

assert: Used to debug, the form checks a condition that is a boolean expression; failure to pass the condition at run time causes an AssertionError. By default the use of assertions is disabled; it can be enabled either on the command line or programmatically.

catch: Serves to take and deal with exceptions created from the use of try statements together with catch.

and lastly: Specifies a block of code that will definitely execute at the end of a try block and any catch clauses connected with the try block provided whether an exception was thrown or caught.

Enumeration

enum: Provides an enumerated (unchangeable) type is a special class that represents a set of named constants.

Keywords The Other Keywords

super Commonly accessed using super: The immediate superclass (parent) object of the current class, used to access overridden methods and hidden members of its superclass or to delegate a call to one constructor to a constructor in the superclass.

this: this is the existing object instance of a method or constructor where it is applied in order to access a member of the object or to pass a call on by one constructor of a class to another constructor of the same class.

Contextual Keywords (introduce in Java 9 and Later)

Contextual keywords, which only have limited scopes, represent some identifiers.

exports: Defines which packages inside a module are exposed, and can be seen by other modules.

module: Defines a module, a self-descriptive agglomeration of code and data, used to package and open only the public interface of a library.

open: It means that the contents of a module are available in reflection at runtime.

Literal Values Words

Such words refer to literal values used by the language and cannot be used as an identifier in the programs.

true: A logical-truth literal value.

false: A literal of boolean type denoting logical false.

null: A literal value of a reference to nothing.

Keywords that are not in use and obsolete

There are keywords, which are not in use at the moment and do not serve a purpose.

const: Java does not use it, it is used to define constants with final.

goto: Not used in Java, whereas it has no functionality.

On Java 9, _ (underscore) became a Java keyword and may no longer be used as a variable name. It is put aside to be used.

Conclusion

This is because of the fact that a developer cannot be a master in Java without the mastering of Java keywords as these are the basic building blocks of Java. The guide is an informative concept to understand every single keyword in the language so that a developer can produce an accurate and effective syntax of Java. Uncodemy provides elite-level programs conducted by competent tutors that aim at enhancing the knowledge of Java and creating a strong foundation that will get the student/student equipped with skills to code which is a practical benefit as they progress into a career.