面试题与答案

The another long-term support(LTS) release for the Java SE platform is Java 17 LTS. The previous LTS version was Java 11. Under the Oracle No-Fee Terms and Conditions License, JDK 17 binaries are free to use in production and redistribute at no cost with the help of OpenJDK. LTS stands for long-term support. It is available from September, 2021. For OracleJDK it is mandatory to purchase the license but it is absolutely free to use OpenJDK.

To check the detail difference, please check here: OracleJDK vs OpenJDK 💯💯

The new features added in Java 17 are as follows:

• Restore or Rebuild the "Always-Strict Floating-Point" Semantics
• Enhanced faster the "pseudo-Random" Number Generators
• New macOS rendering pipelines
• macOS/AArch64 Port
• Dismiss the Applet API for Removal
• JDK Internals Encapsulate strongly
• Switch Pattern Matching (Preview)
• Activation of the Removal RMI
• Generate sealed Classes
• Removal of the Experimental AOT and JIT Compiler
• Remove the Security Manager.
• Foreign Functions and Memory API (Incubator)
• Vector API (Second Incubator)
• Deserialization Filters Based on Context (content-specific)

This JEP makes floating-point operations uniformly stringent and is primarily intended for scientific applications. Both default floating-point operations, strict or strictfp, provide the same outcomes for calculations using floating-point on every platform.

Most browsers will no longer support the applet API because it has been deprecated since JDK9.

Java 17 version marked it for removal even though it has been marked as deprecated since version 9.

RMI's use in the web technology of the previous ten years has rendered the RMI activation mechanism outdated.

Marked for removal in version 15, this JEP removed the RMI activation API from the platform in version 17.

Introduced into JDK 9 and JDK 10, respectively, as experimental features, the Ahead-Of-Time (AOT) compilation and Just-In-Time (JIT) compiler from GraalVM were features with a high cost of maintenance.

Taken out the trial versions of the java-based AOT (ahead-of-time) and JIT (just-in-time) compilers from Java 17.

It makes switch statements and expressions more flexible and expressive by letting patterns appear in case labels. It also makes it possible to relax the switch's null-hostility when needed.

There are two main patterns, which are as follows:

• Guarded pattern: Uses pattern && boolean expression to refine further.
• Pattern between parentheses

static record Human (String name, int age, String profession) {}

public String checkValue(Object obj) {
    return switch (obj) {
        case Human h -> "Name: %s, age: %s and profession: %s".formatted(h.name(), h.age(), h.profession());
        case Circle c -> "This is a circle";
        case Shape s -> "It is just a shape";
        case null -> "It is null";
        default -> "It is an empty";
    };
}

public String checkShape(Shape shape) {
    return switch (shape) {
        case Triangle t && (t.getNumberOfSides() != 3) -> "This is a weird triangle";
        case Circle c && (c.getNumberOfSides() != 0) -> "This is a weird circle";
        default -> "Just a normal shape";
    };
}

You can download Java 17 from the Oracle website: https://www.oracle.com/java/technologies/downloads/#java17