---
title: Java 20
description: JDK 20
category: Java
tag:
- Java
head:
- - meta
- name: keywords
content: Java 20,JDK20,,,,JEP
---
JDK 20 2023 3 21
LTS 2023 9 JDK 21
JDK 20 7
- [JEP 429: Scoped Values](https://openjdk.org/jeps/429)
- [JEP 432: Record Patterns](https://openjdk.org/jeps/432)
- [JEP 433: Pattern Matching for switchswitch ](https://openjdk.org/jeps/433)
- [JEP 434: Foreign Function & Memory API API](https://openjdk.org/jeps/434)
- [JEP 436: Virtual Threads](https://openjdk.org/jeps/436)
- [JEP 437: Structured Concurrency](https://openjdk.org/jeps/437)
- [JEP 438: Vector API API](https://openjdk.org/jeps/438)
JDK 8 JDK 25
## JEP 429: Scoped Values
Scoped Values
```java
final static ScopedValue V = new ScopedValue();
// In some method
ScopedValue.where(V, )
.run(() -> { ... V.get() ... call methods ... });
// In a method called directly or indirectly from the lambda expression
... V.get() ...
```
[](https://www.happycoders.eu/java/scoped-values/)
## JEP 432: Record Patterns
Record Patterns record Record Class
instanceof switch
instanceof
```java
record Shape(String type, long unit){}
```
```java
Shape circle = new Shape("Circle", 10);
if (circle instanceof Shape shape) {
System.out.println("Area of " + shape.type() + " is : " + Math.PI * Math.pow(shape.unit(), 2));
}
```
```java
Shape circle = new Shape("Circle", 10);
if (circle instanceof Shape(String type, long unit)) {
System.out.println("Area of " + type + " is : " + Math.PI * Math.pow(unit, 2));
}
```
switch
```java
interface Shape {}
record Circle(double radius) implements Shape { }
record Square(double side) implements Shape { }
record Rectangle(double length, double width) implements Shape { }
```
```java
Shape shape = new Circle(10);
switch (shape) {
case Circle c:
System.out.println("The shape is Circle with area: " + Math.PI * c.radius() * c.radius());
break;
case Square s:
System.out.println("The shape is Square with area: " + s.side() * s.side());
break;
case Rectangle r:
System.out.println("The shape is Rectangle with area: " + r.length() * r.width());
break;
default:
System.out.println("Unknown Shape");
break;
}
```
```java
Shape shape = new Circle(10);
switch(shape) {
case Circle(double radius):
System.out.println("The shape is Circle with area: " + Math.PI * radius * radius);
break;
case Square(double side):
System.out.println("The shape is Square with area: " + side * side);
break;
case Rectangle(double length, double width):
System.out.println("The shape is Rectangle with area: " + length * width);
break;
default:
System.out.println("Unknown Shape");
break;
}
```
`null` `NullPointerException`
Java 19 [JEP 405](https://openjdk.org/jeps/405) JDK 20 [JEP 432](https://openjdk.org/jeps/432)
-
- `for`
-
**** [JDK16](./java16.md)
## JEP 433: Pattern Matching for switchswitch
`instanceof` `switch`
`instanceof`
```java
// Old code
if (o instanceof String) {
String s = (String)o;
... use s ...
}
// New code
if (o instanceof String s) {
... use s ...
}
```
`switch`
```java
// Old code
static String formatter(Object o) {
String formatted = "unknown";
if (o instanceof Integer i) {
formatted = String.format("int %d", i);
} else if (o instanceof Long l) {
formatted = String.format("long %d", l);
} else if (o instanceof Double d) {
formatted = String.format("double %f", d);
} else if (o instanceof String s) {
formatted = String.format("String %s", s);
}
return formatted;
}
// New code
static String formatterPatternSwitch(Object o) {
return switch (o) {
case Integer i -> String.format("int %d", i);
case Long l -> String.format("long %d", l);
case Double d -> String.format("double %f", d);
case String s -> String.format("String %s", s);
default -> o.toString();
};
}
```
`switch` Java17Java18Java19 Java20
## JEP 434: Foreign Function & Memory API API
Java API Java JVM JVM API Java JNI
API Java 17 [JEP 412](https://openjdk.java.net/jeps/412) Java 18 [JEP 419](https://openjdk.org/jeps/419) Java 19 [JEP 424](https://openjdk.org/jeps/424)
JDK 20 [JEP 434](https://openjdk.org/jeps/434)
- `MemorySegment` `MemoryAddress`
- `MemoryLayout`
- `MemorySession``Arena``SegmentScope`
[Java 19 ](./java19.md) API
## JEP 436: Virtual Threads
Virtual Thread JDK OS Lightweight ProcessLWP JVM
`java.lang.Thread` JVM
[How to Use Java 19 Virtual Threads](https://medium.com/javarevisited/how-to-use-java-19-virtual-threads-c16a32bad5f7)
Windows Linux Java Solaris HotSpot VM Solaris R : [JVM ](https://www.zhihu.com/question/23096638/answer/29617153)
Go GoroutineErlang
Java 19
Java
- [](https://javaguide.cn/java/concurrent/virtual-thread.html)
- [Java19 GA](https://mp.weixin.qq.com/s/yyApBXxpXxVwttr01Hld6Q)
- [ - VirtualThread ](https://www.cnblogs.com/throwable/p/16758997.html)
Java 19 [JEP 425](https://openjdk.org/jeps/425)JDK 20
```java
// 1 Thread.ofVirtual()
Runnable fn = () -> {
// your code here
};
Thread thread = Thread.ofVirtual(fn)
.start();
// 2 Thread.startVirtualThread()
Thread thread = Thread.startVirtualThread(() -> {
// your code here
});
// 3 Executors.newVirtualThreadPerTaskExecutor()
var executorService = Executors.newVirtualThreadPerTaskExecutor();
executorService.submit(() -> {
// your code here
});
class CustomThread implements Runnable {
@Override
public void run() {
System.out.println("CustomThread run");
}
}
//4 ThreadFactory
CustomThread customThread = new CustomThread();
//
ThreadFactory factory = Thread.ofVirtual().factory();
//
Thread thread = factory.newThread(customThread);
//
thread.start();
```
4 `Thread`
## JEP 437: Structured Concurrency
Java 19 API `java.util.concurrent`
API [`StructuredTaskScope`](https://download.java.net/java/early_access/loom/docs/api/jdk.incubator.concurrent/jdk/incubator/concurrent/StructuredTaskScope.html)`StructuredTaskScope`
`StructuredTaskScope`
```java
try (var scope = new StructuredTaskScope()) {
// fork
Future future1 = scope.fork(task1);
Future future2 = scope.fork(task2);
//
scope.join();
//
... process results/exceptions ...
} // close
```
JDK
JDK 20 `StructuredTaskScope` [JEP 429](https://openjdk.org/jeps/429)
## JEP 438: Vector API API
API CPU
API
Vector API [JEP 338](https://openjdk.java.net/jeps/338) [ API](http://openjdk.java.net/jeps/11) Java 16 [JEP 414](https://openjdk.java.net/jeps/414) Java 17 [JEP 417](https://openjdk.java.net/jeps/417) Java 18 [JEP 426](https://openjdk.java.net/jeps/426) Java 19
Java20 API [JEP 438](https://openjdk.org/jeps/438)