java-14

问题 I have a record and want to add default constructor to it. public record Record(int recordId) { public Record { } } But it created constructor with int param. public final class Record extends java.lang.Record { private final int recordId; public Record(int); //other method } How can we add a default constructor to a record? 回答1: To split hairs, you cannot ever define a default constructor, because a default constructor is generated by the compiler when there are no constructors defined, thus

问题 I have a record and want to add default constructor to it. public record Record(int recordId) { public Record { } } But it created constructor with int param. public final class Record extends java.lang.Record { private final int recordId; public Record(int); //other method } How can we add a default constructor to a record? 回答1: To split hairs, you cannot ever define a default constructor, because a default constructor is generated by the compiler when there are no constructors defined, thus

问题 Closed. This question needs debugging details. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 hours ago . I came across this amazing topic on https://www.baeldung.com/java-pattern-matching-instanceof. But when I try to run the following code, it throws compile time error: if(obj instanceof String s) { System.out.println(s); } I am using Java 14. 回答1: This is a preview feature in Java 14, see JEP 305 and

问题 Closed. This question needs debugging details. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 hours ago . I came across this amazing topic on https://www.baeldung.com/java-pattern-matching-instanceof. But when I try to run the following code, it throws compile time error: if(obj instanceof String s) { System.out.println(s); } I am using Java 14. 回答1: This is a preview feature in Java 14, see JEP 305 and

问题 I want to put the flag -XX:+ShowCodeDetailsInExceptionMessages to enable helpful NPEs (https://openjdk.java.net/jeps/358) on the tests I tried tasks.withType<Test> { jvmArgs("-XX:+ShowCodeDetailsInExceptionMessages") testLogging { setExceptionFormat("full") // Prints the message of the exception } } But the NPEs have still no messages. Here's my java version java -version openjdk version "14.0.1" 2020-04-14 OpenJDK Runtime Environment (build 14.0.1+7) OpenJDK 64-Bit Server VM (build 14.0.1+7,

问题 I want to put the flag -XX:+ShowCodeDetailsInExceptionMessages to enable helpful NPEs (https://openjdk.java.net/jeps/358) on the tests I tried tasks.withType<Test> { jvmArgs("-XX:+ShowCodeDetailsInExceptionMessages") testLogging { setExceptionFormat("full") // Prints the message of the exception } } But the NPEs have still no messages. Here's my java version java -version openjdk version "14.0.1" 2020-04-14 OpenJDK Runtime Environment (build 14.0.1+7) OpenJDK 64-Bit Server VM (build 14.0.1+7,

问题 I’m hoping that Java 14 records actually use less memory than a similar data class. Do they or is the memory usage the same? 回答1: To add to the basic analysis performed by @lugiorgi and a similar noticeable difference that I could come up with analyzing the byte code, is in the implementation of toString , equals and hashcode . On one hand, previously used class with overridden Object class APIs looking like public class City { private final Integer id; private final String name; // all-args,

问题 I’m hoping that Java 14 records actually use less memory than a similar data class. Do they or is the memory usage the same? 回答1: To add to the basic analysis performed by @lugiorgi and a similar noticeable difference that I could come up with analyzing the byte code, is in the implementation of toString , equals and hashcode . On one hand, previously used class with overridden Object class APIs looking like public class City { private final Integer id; private final String name; // all-args,

问题 I love project Lombok but in these days I'm reading and trying some of the new features of java 14. Inside the new capability, there is the record keyword that allows creating a class with already built-in the following functionality: constructor, private final fields, accessors, equals/hashCode, getters, toString methods. Now my question is: is better to rely on the feature of Lombok or should we start using the record functionality: Is better to use this: record Person (String name, String

问题 I am trying to have a pom.xml file with PMD plugin integrated into build stage. PMD version 3.13.0 Oracle JDK 14 <?xml version="1.0" encoding="UTF-8"?> <project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>group</groupId> <artifactId>artifact</artifactId> <version>1.0-SNAPSHOT</version> <packaging>jar