October 3, 2023


Develop Technology For The Connected World

Rust programming for Java developers

7 min read

Amid the more recent programming languages rising in recognition is Rust. Rust was initial introduced in 2010 and has quietly gained mindshare for its performance, syntax, and thread security features. If you are a Java developer, you will find Rust rather uncomplicated to get a grip on, many thanks to the similarity of the two languages.

Rust has climbed the ladder of language recognition, or most generally employed languages, but most tellingly, Rust frequently tops out as the the “most beloved language” of all, according to the Stack Overflow survey. That is a testament to the good practical experience of utilizing Rust.

Browse on for a appear at some of the main matters to know about Rust if you are coming from a Java history.

Rust syntax

Like Java, Rust is compiled. It is compiled to the LLVM spec, similar in spirit to the JVM, making it possible for for output to a assortment of target platforms.

And like Java, Rust descends from the C lineage. Its use of curly braces for blocks and semi-colons for line terminations is particularly the same as Java. For example, you can see a basic plan in this article, like Listing 1.

Listing 1. Simple Rust code

fn key() 
println!("Hello there, InfoWorld!")

Recognize that there is a major()function, very similar to the entry point in Java.

Features in Rust

Capabilities stand by yourself in Rust, and they can be declared any place, which include nested in other functions. This is in contrast to Java, the place functions are generally declared as solutions on objects (apart from in the circumstance of lambdas). Set another way, in Java every little thing is an object. Not so in Rust.

Listing 2. Utilizing features in Rust

fn most important() 
println!("Hello, planet!")

fn purpose2()
println!("Hello InfoWorld")



fn purpose3()
println!("Hi once again.")

Implicit return values

Contrary to Java, Rust permits you to skip the return keyword at the stop of a operate. The final assertion in the operate will mechanically be evaluated as the return price. When undertaking this, you omit the semicolon from the final statement.


Like Java, Rust supports lambdas for purposeful type coding. The syntax is unique, but it is not tough to comprehend if you are common with the Java streams API. Listing 3 exhibits the use of the map() perform to make a set of strings uppercase. As you can see, it’s pretty related to Java.

Listing 3. Useful sorting with lambdas

// Rust
fn most important()
enable animals = ["dog", "badger", "quokka"]

enable consequence = animals.iter().map(

The map() operate takes a two-aspect argument. The initially portion is a variable inside the pipe figures, |price|, which will define the variable that is utilised as a cope with on each individual merchandise. The second part is the procedure to execute. In this scenario, we phone to_uppercase() on each individual aspect of the array.

Be aware that, like Java, Rust lambdas are closures that seize the state of the bordering block. In other terms, they have access to the variable context in which they execute.

Objects are structs in Rust

Have a glimpse at Listing 4, which introduces the struct key word. A struct, which is small for composition, lets you to define a container for data, just like the point out aspect of a class in Java.

Listing 4. Working with a Rust struct

struct Animal 
name: String

fn major()
enable doggy = Animal
title: String::from("Shiba")

println!("", doggy.title)

You determine the members of the struct inside of the curly brace of the struct. These variables are analogous to public customers.

See that in the line where by you declare the pet dog variable, no contact to a new key word is necessary. Rust can deduce from the context that a new reference is in purchase.

Next, notice that the title variable is set at generation time to be a string with a price. This is performed by way of calling the crafted-in String.from process using the double-colon reference operator.

Lastly, observe that just like Java, Rust employs the dot operator to accessibility the name area on the dog occasion: puppy.identify.


You can add features to structs, and these functions behave in a lot the same way as methods in Java. For illustration, to insert a discuss() strategy to the Animal struct proven in Listing 4, you can use the impl keyword as seen in Listing 5.

Listing 5. Introducing a strategy

impl Animal 
fn talk(&self)
println!("", self.title)

Impl implies implementation. Here in Listing 5, we are applying the Animal struct. We define a one process, speak, that usually takes a one argument. This argument is the specific &self pointer (the ampersand in Rust usually means the argument is a reference). This exclusive pointer has incredibly comparable semantics to the this key word in Java. It refers to the at present active object occasion.

Calling canine.speak() will output the identify of the existing instantiated item, which is "Shiba" in this instance.

Mutability in Rust

A person of the additional curious factors about Rust, if you’re coming from a Java track record, is the default immutability of variables. In shorter, when you declare a variable in Rust, it is by default immutable, and makes an attempt to alter it will result in an mistake.

To make a variable mutable, the mut keyword need to be added, but mut can only be added by just one reference at a time. Recall, Rust is really anxious with trying to keep code thread-secure. This also avoids concurrent modification faults viewed in Java.

Listing 6 exhibits how to make the canine item mutable, and then assign a new title to it.

Listing 6. A mutable string

enable mut dog = Animal
identify: String::from("Shiba")

dog.name = String::from("Suki")
println!("", canine.title)

The important in this article is the mut search term included to the declaration.

Kind inference in Rust

In Rust, you really don’t normally have to notify the compiler what type of variable you are declaring. This will feel odd for builders coming from Java, exactly where there’s no facility for inferring the variable variety. For case in point, in Listing 7, the compiler correctly infers the type to be integer.

Listing 7. Type inference case in point

allow variety1 = 10
allow number2 = 10
println!("", quantity1 * amount2)

Shadowing and variable names

A different Rust aspect that may well shock a Java developer is what is named variable shadowing. In essence, in its place of declaring a variable as mutable, you can produce a mask on prime of it with the exact same title.

This is a form of one particular-off mutability that generates a new space for the exact variable identify. In general, the means to reuse the exact same variable identify is distinctive from Java. Listing 8 reveals a simple illustration of variable shadowing.

Listing 8. Variable shadowing

fn key() 
    let x = 5
    enable x = x + 1
    println!("The value of x is: ", x) // outputs 6

The tuple kind in Rust

Rust supports a tuple kind, which is a variety of compound variable that does not have a genuine analog in Java. Listing 9 shows you an example of a tuple in motion.

Listing 9. Applying the tuple style

fn key() 
    let myTuple = ("Sum", 10, 5)
    enable (x, y) = myTuple
    println!("The is: ", x, y + z)

Here you can see the myTuple variable is declared with the parentheses made up of a few values, a string and two integers. This is a tuple.

You can “destructure” the tuple into scalar variables as found in the future line, the place the let key phrase is utilized to populate every single variable, x, y, and z, with the values from the tuple.

You can also access the tuple customers by index. For instance, tup. references the first field on the tuple (the string "Sum").

Traits and generics in Rust

In Rust there is the strategy of characteristics, which are similar to high-quality-grained interfaces in Java: They determine what homes a sort shares with other kinds. Set another way, characteristics summary popular operation across various types.

Generics in Rust operate in the same way to individuals in Java, utilizing a comparable angle-bracket syntax, for addressing sorts in a standard way centered on their shared homes.

Take a look at Listing 10, which summarizes an case in point of making use of attributes from the Rust handbook.

Listing 10. Employing a trait

pub trait Summary 
    fn summarize(&self) -> String

pub struct NewsArticle
    pub headline: String,
    pub site: String,
    pub author: String,
    pub content material: String,

impl Summary for NewsArticle
    fn summarize(&self) -> String
        format!(", by ()", self.headline, self.writer, self.place)

pub struct Tweet
    pub username: String,
    pub content material: String,
    pub reply: bool,
    pub retweet: bool,

impl Summary for Tweet
    fn summarize(&self) -> String
        format!(": ", self.username, self.written content)

fn major()
    allow tweet = Tweet
        username: String::from("canine_put up"),
        written content: String::from("A Shih Tzu is scaled-down than a Lurcher",
        reply: phony,
        retweet: bogus,

    println!("1 new tweet: ", tweet.summarize())

Right here the trait keyword is employed to outline a Summary assets, which is then implemented for every single sort, NewsArticle and Tweet, making use of the impl search term. So this is extremely similar to an interface in Java, other than that in Java an interface defines the surface of a full course, in its place of piecemeal defining techniques.

A not so peculiar brew

While this is a quick tour of some of the most salient points for a Java dev new to Rust, you can see that the language is not terribly difficult to strategy. It is usually great to continue to keep an open up mind about new technological know-how, and Rust endorses itself with it’s reliable developer gratification ratings.

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