What is the difference between scala and java

Difference: 1. Java needs to explicitly use return to return the value; while scala's return is optional. 2. Class and method modifiers, scala defaults to public, and java defaults to protected. 3. Java supports interfaces; Scala does not support interfaces and uses traits.

The operating environment of this tutorial: windows7 system, java8 version, DELL G3 computer.

Introduction to Scala

1. What is Scala

Scala is a multi-paradigm programming language designed to The original intention was to integrate various features of object-oriented programming and functional programming. Scala runs on the Java platform (Java Virtual Machine) and is compatible with existing Java programs.

2. Why should you learn Scala

1. Elegance: This is the first issue that framework designers must consider. The users of the framework are application development programmers. Whether the API is elegant or not directly affects the user experience.

2. Fast speed: Scala language has strong expressive ability, one line of code is worth several lines of Java, and the development speed is fast; Scala is statically compiled, so it is much faster than JRuby and Groovy.

3. Can be integrated into the Hadoop ecosystem: Hadoop is now the de facto standard for big data. Spark is not meant to replace Hadoop, but to improve the Hadoop ecosystem. Most of the JVM languages ​​​​may think of Java, but the API made by Java is too ugly, or it is too laborious to implement an elegant API.

Introduction to Java

1. What is Java?

Java is an object-oriented programming language that not only absorbs It takes advantage of the various advantages of the C language and also abandons the concepts such as multiple inheritance and pointers that are difficult to understand in C. Therefore, the Java language has two characteristics: powerful functions and simplicity and ease of use. As a representative of static object-oriented programming languages, Java language perfectly implements object-oriented theory and allows programmers to perform complex programming with an elegant way of thinking.

2. Why should you learn Java?

Java has simplicity, object-oriented, distributed, robustness, security, platform independence and portability, and many Threading, dynamics and other characteristics [2]. Java can write desktop applications, Web applications, distributed systems and embedded system applications, etc.

Table comparison between java and scala

-----	java	scala
Method return value	Java needs to explicitly use return to return the value.	scala's return is optional, and the method call will automatically return the last evaluated expression. If scala uses return, it needs to display the return value of the specified method
The default value of class and method modifiers	The default value of java is protected.	The default scala is public
The default imported class	java imports the java.lang package by default	scala imports the java.lang package and scala package by default, scala.Predef class.
Interface	Java supports interface	Scala does not support interface and uses trait (similar to abstract class in Java).
Class members and singleton objects	Java consists of class members, and singleton objects need to be implemented by themselves.	Scala language mechanism supports singleton objects, companion objects, and companion classes. Companion classes and companion objects need to be used in a class file. When using a companion object, the system implicitly calls apply to generate an object of a companion instance.

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