Marking is effectively the declaration of a new reference to an object. Like declaring a new global variable.Developers often track issues where they literally write on a piece of paper the object ID (or pointer value) for an object they're looking at. With object marking, we can give an instance a specific global name. We can then reference that instance out of any scope...E.g., when you're debugging and want to make sure that the object you're looking at in a method is the one that will be sent to another method (and not a cloned copy). Just mark the object with a name. Then, in the other method, compare the argument to the marked object.You can use this in conditional breakpoints to stop at the right location. It's an amazingly useful feature.
Thread.currentThread() == MyThread_DebugLabel
new HashMap<>(1000); //It will not allow you to put 1000 elements without rebalancing HashMap.newHashMap(1000); // we will have 2048 buckets with threshold of 1334
It’s just the nearest number to the power of 2. So, if you pass 1000 to the constructor (new HashMap<>(1000)), 1024 buckets will be created.
IntelliJ IDEA has a feature called “Live Templates” that allows you to quickly insert predefined code snippets using keyboard shortcuts. For example, you can type “sout” and press the Tab key to automatically expand it into a System.out.println() code block. You can customize and create your own live templates in the IntelliJ IDEA configuration.
As you can see, IntelliJ already has several predefined sections depending on the programming language we are using, but we can also create our own section with the “+” symbol that appears on the right side of the window.
In my case I have selected java and clicked on the add button (“+”) to add a new live template to this group, and then a new window will open asking us for the abbreviation of our shortcut, a description if we wish and the part of the code that corresponds to our new shortcutIn this example we have created a Live Template to declare a logger in the class we want and in this way import it by simply typing in our code “log” and pressing the enter key to set it. As you can see, we have indicated the abbreviation with which we will call this shortcut (“log”), a brief description and then in “Edit variables” we have given value to the variable declared in the expression $CLASS_NAME$
To create a custom live template, go to Settings > Editor > Live Templates. Click the "+" icon to add a new template. Enter an abbreviation, a description, and the template text, then click "OK".
public static void main(String[] args) {$END$}
Now, when you type “main” and press Tab, the main method will be inserted, and your cursor will be placed at the $END$ position.
The method String translateEscapes() returns a new String with escape sequences translated if present in the original string.
String s = "java\\nhello\\tword";
System.out.println(s); // Output: java\nhello\tword
System.out.println(s.translateEscapes());
// Output:
// java
// hello wordThe join method offers the convenience of not adding the delimiter at the end of the string as well.
public static String join(CharSequence delimiter, CharSequence... elements)
public static String join(CharSequence delimiter, Iterable<? extends CharSequence> elements)String joined = String.join("-", "java", "programming", "hello", "world");
System.out.println(joined); // Output: java-programming-hello-world
String joined2 = String.join("", "java", "programming", "hello", "world");
System.out.println(joined2); // Output: javaprogramminghelloworldList<String> list = List.of("java", "programming", "hello", "world");
String joined = String.join(", ", list);
System.out.println(joined); // Output: java, programming, hello, worldpublic <R> R transform(Function<? super String, ? extends R> f)Function<String, String> titleCase = s ->
Character.toUpperCase(s.charAt(0)) + s.toLowerCase().substring(1);
System.out.println("animal".transform(titleCase)); // Animal
Function<String, Integer> converToInt = Integer::parseInt;
int num = "123".transform(converToInt);
System.out.println(num); // 123String poem = "Two loves I have of comfort and despair,\n" +"Which like two spirits do suggest me still:\n" +"The better angel is a man right fair,\n" +"The worser spirit a woman color’d ill.\n";System.out.println(poem);System.out.println(poem.indent(4));System.out.println(poem.indent(10));Two loves I have of comfort and despair,Which like two spirits do suggest me still:The better angel is a man right fair,The worser spirit a woman colord ill.Two loves I have of comfort and despair,Which like two spirits do suggest me still:The better angel is a man right fair,The worser spirit a woman colord ill.Two loves I have of comfort and despair,Which like two spirits do suggest me still:The better angel is a man right fair,The worser spirit a woman colord ill.
Repeats the String as many times as provided by the int parameter
public String repeat(int count)String str = "...";
String repeatedStr = StringUtils.repeat(str, 3);
String repeatedStr2 = str.repeat(3);
System.out.println("java".repeat(5)); // javajavajavajavajava
System.out.println("apple, ".repeat(4)); //apple, apple, apple, apple,
System.out.println("*".repeat(10)); // *********String str = "abc";
String repeated = str.repeat(3);
repeated.equals("abcabcabc");Uses a Spliterator to lazily provide lines from the source string
public Stream<String> lines()String output = paragraph.lines().collect(Collectors.joining());String sentence = "marry\n had\n a\n little\n lamb";
Stream<String> lineStream = sentence.lines();
lineStream.forEach(System.out::println);
// marry
// had
// a
// little
// lamb
System.out.println("The sentence has a total of " + sentence.lines().count() + " lines");
// The sentence has a total of 5 linesimport org.testcontainers.containers.Neo4jContainer;
import org.testcontainers.utility.DockerImageName;Neo4jContainer<?> container = new Neo4jContainer<>(DockerImageName.parse("neo4j:5.5.0")).withoutAuthentication();String url = container.getBoltUrl()
import org.testcontainers.containers.output.Slf4jLogConsumer;
public static final Neo4jContainer<?> container =
new Neo4jContainer<>(DockerImageName.parse("neo4j:5.5.0"))
.withoutAuthentication()
.withLogConsumer(new Slf4jLogConsumer(LOGGER).withPrefix("Docker"));<dependency><groupId>org.apache.kafka</groupId><artifactId>connect-api</artifactId><version>2.8.2</version></dependency>
implementation group: 'org.apache.kafka', name: 'connect-api', version: '...'
import org.apache.kafka.connect.connector.ConnectorContext;import org.apache.kafka.connect.source.SourceConnector;import org.apache.kafka.connect.source.SourceRecord;import org.apache.kafka.connect.source.SourceTask;import org.apache.kafka.connect.source.SourceTaskContext;import org.apache.kafka.connect.storage.OffsetStorageReader;public class MyKafkaConnectSource<T> {private final SourceConnector connector;private final SourceTask task;private final Map<String, String> taskConfig;public void process() {if (!taskInit) {task.initialize(...);task.start(taskConfig);taskInit = true;}try {List<SourceRecord> records = task.poll();if (records == null) {return;}for (SourceRecord record : records) {...}} catch (InterruptedException e) {...}}}
We just create a file inside root folder of the app, type any name we want and add .http extension at the end. HTTP request syntax is pretty simple.
// Add new product to the databasePOST http://localhost:8080/api/v1/adminContent-Type: application/jsonAccept: application/json{"brand": "Bombbar","category": "cookie","name": "Protein cookie","flavour": "Chocolate brownie","caloriesPer100Gram": 271,"weight": 40}###// Get info about the product from the databaseGET http://localhost:8080/api/v1/client?brand=BombbarAccept: application/json
POST http://localhost:8080/clients
Content-Type: application/json
{
"clientId": "my-trusted-ui",
"clientSecret": "Passw0rd#",
"scope": "read, write",
"authorizedGrantTypes": "password,refresh_token",
"authorities": "USER,BUSINESS",
"accessTokenValidity": 93601,
"refreshTokenValidity": 604801,
"additionalInformation": "none"
}import java.lang.AssertionError;
class Example { private Example() { throw new AssertionError(); } }
FlightRecorderMXBean flightRecorder = ManagementFactory .getPlatformMXBean(FlightRecorderMXBean.class); long recordingId = flightRecorder.newRecording(); flightRecorder.startRecording(recordingId); // Perform some operations flightRecorder.stopRecording(recordingId);
HttpClient client = HttpClient.newHttpClient(); HttpRequest request = HttpRequest.newBuilder() .uri(URI.create("https://...")) .GET() .build(); HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString()); System.out.println(response.body());
HttpClient httpClient = HttpClient.newBuilder() .version(HttpClient.Version.HTTP_2) .connectTimeout(Duration.ofSeconds(20)) .build(); HttpRequest httpRequest = HttpRequest.newBuilder() .GET() .uri(URI.create("https://...")) .build(); HttpResponse httpResponse = httpClient.send(httpRequest, HttpResponse.BodyHandlers.ofString()); System.out.println(httpResponse.body());