John Bach - Learning Java: Beginning programming with java for dummies

Learning Java Beginning Programming with Java For Dummies By John Bach For information contact : (alabamamond@gmail.com, memlnc) http://www.memlnc.com First Edition: july 2020 UNITY GAME PROGRAMMING Copyright 2020 by ALEXANDER ARONOWITZ "Programming isn't about what you know; it's about what you can figure out. - Chris Pine 2020 CONTENT Introduction Java Program Execution Basic structures of the Java language A simple program to lang 's ke Java Comments Data types and displaced n nye Constants Big numbers Methods for working with large numbers Operations Converting numeric types Cast Strings Union with t rock Substrings Editing a string Checking strings for equalit y Some methods of the String class Controlling program execution Block scope Conditional statement if - else Multivariate branching - switch statement While and do - while loops cycle for Break statement The continue statement Arrays Copying arrays Sorting arrays Arrays Class Methods Multidimensional array s Command line parameters Cantilever th input-you in odes Objects and Classes Introduction to Object Oriented Programming OOP terminology Differences between OOP and Traditional Procedural Programming Classes New operation An example of using existing classes Constructors Method overloading The this keyword in constructors A note about data encapsulation Static fields and methods Static fields Static methods Initialization blocks Packages Using packages Adding a class to a package Specifying the path to packages Package scope JAR files Class design guidelines Inheritance Extending classes Overriding (overriding) methods Inheritance hierarchy Polymorphism Dynamic linking Preventing Inheritance: Terminal Classes and Methods Abstract classes Protected Access ( protected, ) How to apply inheritance Interfaces Interface operator Implements statement Constants in interfaces Exceptional situations Classification of Exceptions Declaring Method Exceptions How to raise an exceptional situation Creating Exception Classes Catching exceptions ( t ry - catch block ) Catching multiple exceptions Re-raising an exception Finally section How to use exceptions I / O streams Reading and writing bytes Complete family of threads Stream filters Data streams Direct File Streams Text streams Writing text to the output stream Reading text from an input stream Working with files on the th system Letter t hurray
Introduction The Java language was created in the early 90's as part of a software development project for consumer electronic devices. The original new object-oriented programming language was named Oak (oak) . With the development of network Internet language Oak was used to create Internet-applications ( eg, n and this language was written Oak-browser " WebRunner " ) . In 1995, Sun Microsystems decided to announce a new product, renaming it Java (the only reasonable explanation for the name is the love of coffee programmers) , and WebRunner was renamed HotJava . The Java language is now increasingly used to create " middleware " that maintains communication between clients and server resources .

In addition, the Java language has taken over the leadership in embedded systems , becoming the de facto standard for portable devices , on-board car computers, and so on . One of the main advantages of the Java language is independence from the platform on which programs are executed: the same code can be run under Windows , Solaris , Linux , Macintosh , etc. Operating systems . Another advantage is that the syntax of the Java language is similar to the syntax language s C ++ and C . In addition, Java is a completely object-oriented language, even more so than C ++. All entities in the Java language are objects, with the exception of a few primitive types , such as numbers.

In contrast to C ++ , it is easier to develop error-free programs in Java . The Java language provides tools to eliminate the very possibility of creating programs that would hide the most common errors. To do this, the Java language has done the following :

• The possibility of explicit allocation and freeing of memory has been excluded. Java memory is automatically reclaimed by garbage collection. The programmer is guaranteed against errors related to misuse of memory ;
• Introduced true arrays and disallowed pointer arithmetic. Now programmers, in principle, cannot erase data from memory due to improper use of pointers ;
• Eliminated the possibility of confusing the assignment operator with the equality comparison operator .

  Now you can not even compile the expression of the if ( a = 3) { ... } (this error - the source of most confusion in the languages C and C ++).

• Multiple inheritance is excluded. It has been replaced by the concept of interface a , borrowed from Objective C. An interface gives the programmer almost everything a programmer can get from multiple inheritance, while avoiding the complexity of managing class hierarchies .

Java Program Execution A program written in a high-level language (called a source module ) cannot be executed immediately . From the beginning it must be compiled, that is , translated into a sequence of machine instructions - an object module. For boot th unit I of bektny module n uzhno build the libraries used in the module and enable the cross-references between the object module sections The source module written in the language of the Java , could not avoid these procedures, but here is shown the main feature of the technology the Java - the program is compiled directly into machine instructions, but does not command a particular processor, and in the team's so-called in irtualn second machine s the Java ( JVM, Java Virtual Machi ne ).

The Java Virtual Machine is a collection of commands along with their execution system. Note that the virtual machine Java completely stack, and therefore does not require complex th addressing of and memory cells and a large of quantity and registers. By A team JVM short, most of which it has a length of 1 byte, so the JVM command called a byte - code ( bytecodes ), although there are teams of length 2 and 3 bytes. Full description of the commands and the entire JVM architecture is contained in a virtual machine specification the Java (the VMS, the Virtual Machine specifica tion of ). Another feature of Java is that all standard functions that are called in a program are connected to it only at run time, and are not included in the bytecode. In other words, there is dynamic linking ( dynamic binding ) , which significantly reduces the amount of the compiled program.

Since a program written in Java is translated by the compiler into the bytecode of the Java Virtual Machine , it is independent of the type of processor and architecture of the computer being used . Therefore, bytecode can be performed and be on any computer with a system that implements the JVM. In this case, neither the type of processor nor the architecture of the computer is important. T. e language. (Obviously, the implementation of the Java virtual machine is platform dependent.) Bytecode interpretation and dynamic linking slow down program execution significantly. (Obviously, the implementation of the Java virtual machine is platform dependent.) Bytecode interpretation and dynamic linking slow down program execution significantly.

It does not matter when the bytecode before ae tsya on the network - network slower than any interpretation ; however , other situations require a powerful and fast computer. To increase the speed of interpretation p azrabotany JIT-compiler ( " timely " compilers - the Just - with In - Time The compiler ), memories have interpreted sections of code to machine CPU and simply performing these areas when re-treatment, for example, in cycles. Only a specialized processor can provide the highest speed of bytecode execution . The company of SUN Microsystems released the microprocessors picoJava , running on the system JVM command, e nce and Java-processors of other companies. These processors directly execute bytecode. And nterpreta tori JVM commands in a specific processor instructions designed for virtually all computing platforms.

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