Cast arraylist to collection java

Converting Iterable to Collection in Java

Repeatedly, code that works in dev breaks down in production. Java performance issues are difficult to track down or predict.

Simply put, Digma provides immediate code feedback. As an IDE plugin, it identifies issues with your code as it is currently running in test and prod.

The feedback is available from the minute you are writing it.

Imagine being alerted to any regression or code smell as you’re running and debugging locally. Also, identifying weak spots that need attending to, based on integration testing results.

Of course, Digma is free for developers.

As always, the writeup is super practical and based on a simple application that can work with documents with a mix of encrypted and unencrypted fields.

We rely on other people’s code in our own work. Every day.

It might be the language you’re writing in, the framework you’re building on, or some esoteric piece of software that does one thing so well you never found the need to implement it yourself.

The problem is, of course, when things fall apart in production — debugging the implementation of a 3rd party library you have no intimate knowledge of is, to say the least, tricky.

Lightrun is a new kind of debugger.

It’s one geared specifically towards real-life production environments. Using Lightrun, you can drill down into running applications, including 3rd party dependencies, with real-time logs, snapshots, and metrics.

Learn more in this quick, 5-minute Lightrun tutorial:

Slow MySQL query performance is all too common. Of course it is. A good way to go is, naturally, a dedicated profiler that actually understands the ins and outs of MySQL.

The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.

Critically, it has very minimal impact on your server’s performance, with most of the profiling work done separately — so it needs no server changes, agents or separate services.

Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:

DbSchema is a super-flexible database designer, which can take you from designing the DB with your team all the way to safely deploying the schema.

The way it does all of that is by using a design model, a database-independent image of the schema, which can be shared in a team using GIT and compared or deployed on to any database.

And, of course, it can be heavily visual, allowing you to interact with the database using diagrams, visually compose queries, explore the data, generate random data, import data or build HTML5 database reports.

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1. Overview

In this tutorial, we’ll explore different ways to convert an Iterable to a Collection in Java.

We’ll start with plain Java solutions, then have a look at the options that the Guava and Apache Commons libraries also provide.

2. Iterable and Iterator

First, we’ll define our Iterable:

Iterable iterable = Arrays.asList("john", "tom", "jane");

We’ll also define a simple Iterator – to highlight the difference between converting Iterable to Collection and Iterator to Collection:

Iterator iterator = iterable.iterator();

3. Using Plain Java

3.1. Iterable to Collection

We can use the Java 8 forEach() method to add all elements to the List:

@Test public void whenConvertIterableToListUsingJava8_thenSuccess() < Listresult = new ArrayList(); iterable.forEach(result::add); assertThat(result, contains("john", "tom", "jane")); >

Or use the Spliterator class to convert our Iterable to Stream then to Collection:

List result = StreamSupport.stream(iterable.spliterator(), false) .collect(Collectors.toList());

3.2. Iterator to Collection

On the other hand, instead of using forEach(), we’ll use forEachRemaining() with Iterator:

@Test public void whenConvertIteratorToListUsingJava8_thenSuccess() < Listresult = new ArrayList(); iterator.forEachRemaining(result::add); assertThat(result, contains("john", "tom", "jane")); >

We can also create a Spliterator from our Iterator then use it to convert Iterator to Stream:

List result = StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false) .collect(Collectors.toList());

3.3. Using a For-Loop

Let’s also have a look at a solution that uses a very simple for-loop to convert our Iterable to a List:

@Test public void whenConvertIterableToListUsingJava_thenSuccess() < Listresult = new ArrayList(); for (String str : iterable) < result.add(str); >assertThat(result, contains("john", "tom", "jane")); >

On the other hand, we’ll use hasNext() and next() with the Iterator:

@Test public void whenConvertIteratorToListUsingJava_thenSuccess() < Listresult = new ArrayList(); while (iterator.hasNext()) < result.add(iterator.next()); >assertThat(result, contains("john", "tom", "jane")); >

4. Using Guava

There are also a few libraries available that provide convenient methods to help us achieve this.

Let’s see how we can use Guava to convert from an Iterable to a List:

We can create a new List from Iterable or Iterator using Lists.newArrayList():

List result = Lists.newArrayList(iterable);

Or we can use ImmutableList.copyOf():

List result = ImmutableList.copyOf(iterable);

5. Using Apache Commons

Finally, we’ll use Apache Commons IterableUtils to create a List from Iterable:

List result = IterableUtils.toList(iterable);

Similarly, we’ll use IteratorUtils to create a List from our Iterator:

List result = IteratorUtils.toList(iterator);

6. Conclusion

In this short article, we learned how to convert an Iterable and Iterator to a Collection using Java. We explored different ways using plain Java, and two external libraries: Guava and Apache Commons.

As always, the full source code is available over on GitHub.

Slow MySQL query performance is all too common. Of course it is. A good way to go is, naturally, a dedicated profiler that actually understands the ins and outs of MySQL.

The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.

Critically, it has very minimal impact on your server’s performance, with most of the profiling work done separately — so it needs no server changes, agents or separate services.

Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:

Источник

Converting Between a List and a Set in Java

Repeatedly, code that works in dev breaks down in production. Java performance issues are difficult to track down or predict.

Simply put, Digma provides immediate code feedback. As an IDE plugin, it identifies issues with your code as it is currently running in test and prod.

The feedback is available from the minute you are writing it.

Imagine being alerted to any regression or code smell as you’re running and debugging locally. Also, identifying weak spots that need attending to, based on integration testing results.

Of course, Digma is free for developers.

As always, the writeup is super practical and based on a simple application that can work with documents with a mix of encrypted and unencrypted fields.

We rely on other people’s code in our own work. Every day.

It might be the language you’re writing in, the framework you’re building on, or some esoteric piece of software that does one thing so well you never found the need to implement it yourself.

The problem is, of course, when things fall apart in production — debugging the implementation of a 3rd party library you have no intimate knowledge of is, to say the least, tricky.

Lightrun is a new kind of debugger.

It’s one geared specifically towards real-life production environments. Using Lightrun, you can drill down into running applications, including 3rd party dependencies, with real-time logs, snapshots, and metrics.

Learn more in this quick, 5-minute Lightrun tutorial:

Slow MySQL query performance is all too common. Of course it is. A good way to go is, naturally, a dedicated profiler that actually understands the ins and outs of MySQL.

The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.

Critically, it has very minimal impact on your server’s performance, with most of the profiling work done separately — so it needs no server changes, agents or separate services.

Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:

DbSchema is a super-flexible database designer, which can take you from designing the DB with your team all the way to safely deploying the schema.

The way it does all of that is by using a design model, a database-independent image of the schema, which can be shared in a team using GIT and compared or deployed on to any database.

And, of course, it can be heavily visual, allowing you to interact with the database using diagrams, visually compose queries, explore the data, generate random data, import data or build HTML5 database reports.

Источник

Converting Between a List and a Set in Java

Repeatedly, code that works in dev breaks down in production. Java performance issues are difficult to track down or predict.

Simply put, Digma provides immediate code feedback. As an IDE plugin, it identifies issues with your code as it is currently running in test and prod.

The feedback is available from the minute you are writing it.

Imagine being alerted to any regression or code smell as you’re running and debugging locally. Also, identifying weak spots that need attending to, based on integration testing results.

Of course, Digma is free for developers.

As always, the writeup is super practical and based on a simple application that can work with documents with a mix of encrypted and unencrypted fields.

We rely on other people’s code in our own work. Every day.

It might be the language you’re writing in, the framework you’re building on, or some esoteric piece of software that does one thing so well you never found the need to implement it yourself.

The problem is, of course, when things fall apart in production — debugging the implementation of a 3rd party library you have no intimate knowledge of is, to say the least, tricky.

Lightrun is a new kind of debugger.

It’s one geared specifically towards real-life production environments. Using Lightrun, you can drill down into running applications, including 3rd party dependencies, with real-time logs, snapshots, and metrics.

Learn more in this quick, 5-minute Lightrun tutorial:

Slow MySQL query performance is all too common. Of course it is. A good way to go is, naturally, a dedicated profiler that actually understands the ins and outs of MySQL.

The Jet Profiler was built for MySQL only, so it can do things like real-time query performance, focus on most used tables or most frequent queries, quickly identify performance issues and basically help you optimize your queries.

Critically, it has very minimal impact on your server’s performance, with most of the profiling work done separately — so it needs no server changes, agents or separate services.

Basically, you install the desktop application, connect to your MySQL server, hit the record button, and you’ll have results within minutes:

DbSchema is a super-flexible database designer, which can take you from designing the DB with your team all the way to safely deploying the schema.

The way it does all of that is by using a design model, a database-independent image of the schema, which can be shared in a team using GIT and compared or deployed on to any database.

And, of course, it can be heavily visual, allowing you to interact with the database using diagrams, visually compose queries, explore the data, generate random data, import data or build HTML5 database reports.

Источник