Exceptionally completes this CompletableFuture with TimeoutException if not otherwise completed before the given timeout.
ÖrnekŞöyle yaparızCompletableFuture<Void> f1 = ...
CompletableFuture<Void> f2 = f1.orTimeout(TIMEOUT_IN_MILLIS, TimeUnit.MILLISECONDS);
V get() throws InterruptedException, ExecutionException;try {
CompletableFuture.allOf(fanoutRequestList).get()
} catch (InterruptedException | ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}ÖrnekTüm işlerin bitmesini beklemek için şöyle yaparızint TIMEOUT_IN_MILLIS = 100;
@Test
public void allOfOrTimeout() throws InterruptedException, ExecutionException,
TimeoutException {
getAllOfFuture().get(TIMEOUT_IN_MILLIS, TimeUnit.MILLISECONDS);
}
private CompletableFuture<Void> getAllOfFuture() {
return CompletableFuture.allOf(
CompletableFuture.runAsync(() -> sleep(1)),
CompletableFuture.runAsync(() -> sleep(2)),
CompletableFuture.runAsync(() -> sleep(3)),
CompletableFuture.runAsync(() -> sleep(4)),
CompletableFuture.runAsync(() -> sleep(5)),
CompletableFuture.runAsync(() -> sleep(6)),
CompletableFuture.runAsync(() -> sleep(7)),
CompletableFuture.runAsync(() -> sleep(8))
);
}
public static void sleep(int millis) {
try {
Thread.sleep(millis);
System.out.format("Had a nap for %s milliseconds.\r\n", millis);
} catch (InterruptedException e) {
e.printStackTrace();
}
};
Had a nap for 1 milliseconds.
Had a nap for 2 milliseconds.
Had a nap for 3 milliseconds.
Had a nap for 4 milliseconds.
Had a nap for 5 milliseconds.
Had a nap for 6 milliseconds.
Had a nap for 7 milliseconds.
Had a nap for 8 milliseconds.The execution engine has a few sub-components.- Interpreter- Profiler- Java Native Interface- Native Interface Library
Interesting fact: byte-code is called byte-code, as each instruction in byte-code is of byte length, so that it can be loaded into the CPU cache, and in fact there were also java CPUs built!!! didn’t take-off
opcode (1 byte) operand1 (optional) operand2 (optional) ...class Outer {
private class Inner {...}
void foo() {
Inner a = this.new Inner();
Inner b = new Outer.Inner();
Inner c = new Inner(); // Recommended way to write it
}
}0: new #7 // class Outer$Inner
3: dup
4: aload_0
5: invokespecial #9 // Method Outer$Inner."<init>":(LOuter;)V
8: astore_1
9: new #7 // class Outer$Inner
12: dup
13: aload_0
14: invokespecial #9 // Method Outer$Inner."<init>":(LOuter;)V
17: astore_2
18: new #7 // class Outer$Inner
21: dup
22: aload_0
23: invokespecial #9 // Method Outer$Inner."<init>":(LOuter;)V
26: astore_3public static void main(String[] args) {
System.out.println("" == ".".substring(1));
}
0: getstatic #7 // Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #13 // String
5: ldc #15 // String .
7: iconst_1
8: invokevirtual #17 // Method java/lang/String.substring:(I)Ljava/lang/String;
11: if_acmpne 18
14: iconst_1
15: goto 19
18: iconst_0
19: invokevirtual #23 // Method java/io/PrintStream.println:(Z)V
22: returnThis instruction was added in Java 7 with the goal of better support for dynamic languages in the JVM, such as Groovy and JRuby.
Java has introduced byte code instruction invokedynamic to construct the anonymous class and then generate byte code for lambdas. So, In case of lambdas java generates the implementation class and generate byte code at runtime.
In a nutshell, an invokedynamic invocation consists of two phases: looking up a CallSite and then invoking the MethodHandle the CallSite holds. If the same invokedynamic instruction is executed another time, CallSite from the initial lookup will be invoked.
ByteBuffer byteBuffer = ByteBuffer.allocate(64);
byteBuffer.flip(); 0: bipush 64
2: invokestatic #19 // Method java/nio/ByteBuffer.allocate:(I)Ljava/nio/ByteBuffer;
5: astore_1
6: aload_1
7: invokevirtual #25 // Method java/nio/ByteBuffer.flip:()Ljava/nio/ByteBuffer;
10: poppublic static int frequency(Collection<?> c, Object o)Birinci parametre içinde arama yapılacak olan liste, ikinci parametre aranılan nesnedir. p nesnesinin equals metodunu gerçekleştiriyor olması gerekir.Returns the number of elements in the specified collection equal to the specified object. More formally, returns the number of elements e in the collection such that (o == null ? e == null : o.equals(e)).
HashMap<Character, Integer> map = new HashMap<Character, Integer>();ArrayList<Character> list1 = ...ArrayList<Character> list2 = ...for (Character c : list1) {map.put(c, Collections.frequency(list2, c));}
"%JAVA_HOME%\bin\java" ... -Xms256m ...-Xmx2048m -Xms2048m -Xmn768m -XX:PermSize=128m -Xss256k"%JAVA_HOME%\bin\java" ... -Xmx512m ...-Xmx1024k
-Xmx512m
-Xmx8gWhen we launch applications, we specify the initial memory size and maximum memory size. For the applications that run on JVM (Java Virtual Machine), initial and maximum memory size is specified through "-Xms" and "-Xmx" arguments. If Java applications are running on containers, it’s specified through "-XX:InitialRAMPercentage" and "-XX:MaxRAMPercentage" arguments.
Java 10 introduced a new JVM flag — -XX:+UseContainerSupport (set to true by default) which allows the JVM to detect available memory and CPU if it’s running in a container environment, where these resources are limited. This flag works in conjunction with -XX:MaxRAMPercentage which lets set the maximum heap size based on the percentage of the total available memory. In the case of Kubernetes, the limit setting on the container is used as a base of this calculation. For example — if the pod has a limit of 2GB, and the MaxRAMPercentage flag is set to 75%, it’ll result in the maximum heap size of 1500MB.
1. Set the memory request and limit the same. That way you’ll avoid pod eviction due to insufficient node resources. More on this here.
2. Increase pod’s memory limits only in the event of Java OutOfMemory erros. In case of OOMKilled crashes, leave more memory to non-heap usage.
3. Set maximum and initial heap sizes to the same value. That way, you’ll prevent performance penalities in case of heap allocation increases and you’ll ‘fail fast’ if the heap percentage/non-heap memory/pod limits math is wrong. More on this suggestion here.
-XX:MinRAMPercentage seçeneğiSuppose you are configuring -XX:InitialRAMPercentage=25 and overall physical memory (or container memory) is 1GB then your java application’s heap size will be ~250MB (i.e., 25% of 1GB).‘-XX:InitialRAMPercentage’ will be used to derive initial heap size only if ‘-Xms’ JVM argument isn’t passed. If the ‘-Xms’ JVM argument is passed, the ‘-XX:InitialRAMPercentage’ will be ignored by the JVM.