咖啡汪日志——Stream流测试代码，私人笔记，请勿偷看！私人笔记，请勿偷看！私人笔记，请勿偷看！重要的事情说三遍
作者：互联网
1.因式分解
import java.math.BigInteger;
/**
* 进行因式分解的正确姿势
* 每次进行分解的因子，都应该与上次最后一次进行缓存的因子相同
* **
*
* @author: Yuezejian Created in 2020/9/29 上午8:21
* @modified By:
*/
public class CacheFactorizer {
private BigInteger lastNumber;
private BigInteger[] lastFactors;
private long counts;
private long cacheCounts;
public synchronized long getCounts() {return this.counts;}
public synchronized double getCacheCountsRatio() {
return (double) cacheCounts / (double) counts;
}
//TODO:
public void service(Integer counts) {
BigInteger i = BigInteger.valueOf(counts);
BigInteger[] factors = null;
synchronized (this) {
++counts;
if (i.equals(lastNumber)) {
++cacheCounts;
factors = lastFactors.clone();
}
}
if (factors == null) {
factors = factors(i);
synchronized (this) {
lastNumber = i;
lastFactors = factors.clone();
}
}
}
private BigInteger[] factors(BigInteger i) {
return this.lastFactors;
}
}
2.线程优先级
import java.util.stream.IntStream;
/**
* 线程优先级
* **
*
* @author: Yuezejian Created in 2020/9/28 下午8:56
* @modified By:
*/
public class ThreadRank {
public static void main(String[] args) {
Thread thread = new Thread(() -> {
IntStream.rangeClosed(1,100).parallel().forEach( i -> {
System.out.println(Thread.currentThread().getName());
});
},"线程1");
thread.setPriority(Thread.MIN_PRIORITY);
Thread thread1 = new Thread(() -> {
IntStream.rangeClosed(1,20).parallel().forEach(i -> {
System.out.println(Thread.currentThread().getName());
});
},"线程2");
thread.start();
thread.setDaemon(true);
}
//TODO:凡是“线程1”的都是同步执行的，其余的都是异步线程池执行的，1-7共7个执行线程，这是应为stream的并行流parallel使用的是实际可用的核心数-1，本汪猜应该是底层调用了Runtime.accessableProcessor()方法，然后减了一作为执行线程数，因为java中很多地方都是这么处理的，Runtime.accessableProcessor()方法返回的是实际可用的核心数，也包括现代cpu超线程技术所产生的虚拟内核。
//线程1
//ForkJoinPool.commonPool-worker-4
//线程1
//线程1
//线程1
//线程1
//ForkJoinPool.commonPool-worker-1
//线程1
//ForkJoinPool.commonPool-worker-6
//线程1
//ForkJoinPool.commonPool-worker-2
//ForkJoinPool.commonPool-worker-7
//ForkJoinPool.commonPool-worker-4
//ForkJoinPool.commonPool-worker-5
//ForkJoinPool.commonPool-worker-3
//ForkJoinPool.commonPool-worker-7
//ForkJoinPool.commonPool-worker-2
//线程1
//ForkJoinPool.commonPool-worker-6
//ForkJoinPool.commonPool-worker-1
}
import cn.hutool.core.lang.Snowflake;
import com.google.common.collect.Maps;
import com.tjxskj.taidacity.pojo.Coupon;
import org.assertj.core.util.Lists;
import org.junit.Test;
import java.math.BigDecimal;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Predicate;
import java.util.stream.LongStream;
import static java.util.stream.Collectors.*;
/**
* 缓存测试
* **
*
* @author: Yuezejian Created in 2020/10/5 下午3:29
* @modified By:
*/
public class TestCache {
public static final Snowflake snow = new Snowflake(12,10);
ConcurrentHashMap<Long, Coupon> cache;
List<Coupon> list = Arrays.asList(new Coupon(1,new BigDecimal(2)),new Coupon(2,new BigDecimal(3)));
List<Coupon> couponList = Lists.newArrayList(list);
@Test
public void addCache() {
cache = LongStream.rangeClosed(1,10).boxed()
.collect(toConcurrentMap(k -> snow.nextId(),v -> new Coupon(v,new BigDecimal(v)),
(o1, o2) -> o1,ConcurrentHashMap::new));
Map<Long,String> map = Maps.newLinkedHashMap();
cache.entrySet().forEach( entry -> {
// System.out.println(entry.getKey());
// System.out.println(entry.getValue());
});
Predicate<Integer> positiveNumber = i -> i > 0;
Predicate<Integer> evenNumber = i -> i % 2 == 0;
List<Integer> arr = Arrays.asList(1,2,-8,88,-9,-12,25,0,10);
double[] arr1 = arr.stream().filter(i -> i > 0).sorted(Comparator.reverseOrder()).mapToDouble(Integer::doubleValue).toArray();
Arrays.stream(arr1).forEach( i -> {
System.out.println(i);
});
couponList.stream().forEach(i -> {
System.out.println(i.toString());
});
}
}
import com.sun.codemodel.internal.JForEach;
import org.junit.Assert;
import org.junit.Test;
import org.junit.jupiter.api.DisplayNameGeneration;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.IntSupplier;
import java.util.function.Supplier;
import java.util.stream.IntStream;
/**
* Generate测试
* **
*
* @author: Yuezejian Created in 2020/9/30 上午8:48
* @modified By:
*/
public class TestIntStream {
//generate() 返回的是无限流，必须用limit去截取
int sum = IntStream.generate(() -> 123).limit(1).sum();
IntSupplier supplier = () -> 1;
int sum1 = IntStream.generate(supplier).limit(1).sum();
int sum2 = IntStream.rangeClosed(1,4).sum();
int sum3 = IntStream.range(1,4).sum();
int sum4 = IntStream.of(1,4,6,9).sum();
int sum5 = IntStream.empty().sum();
int sum6 = IntStream.builder().add(1).add(10).build().sum();
long sum7 = IntStream.concat(IntStream.range(1,5),IntStream.rangeClosed(1,5)).sum();
int sum8 = IntStream.iterate(1,i -> i + 1).limit(10).sum();
@Test
public void testIntStreamWithAssert() {
Assert.assertEquals(123,sum);
Assert.assertEquals(1,sum1);
Assert.assertEquals(10,sum2);
Assert.assertEquals(6,sum3);
Assert.assertEquals(20,sum4);
Assert.assertEquals(0,sum5);
Assert.assertEquals(11,sum6);
Assert.assertEquals(25,sum7);
}
@Test
public void testInIntStream() {
AtomicInteger count = new AtomicInteger();
IntStream.iterate(2,(e) -> e).limit(10).forEach( i -> {
count.addAndGet(i);
System.out.println(count.get());
});
System.out.println("最终结果"+count);
}
public void testIterator() {
Supplier<AtomicInteger> supplier = AtomicInteger::new;
}
ThreadLocal<Integer> threadLocal = ThreadLocal.withInitial(() -> null);
}
import cn.hutool.core.lang.Snowflake;
import com.google.common.collect.Lists;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.IntSupplier;
import java.util.function.Supplier;
import java.util.stream.Collectors;
import java.util.stream.IntStream;
import java.util.stream.LongStream;
import static java.util.function.Function.identity;
import static java.util.stream.Collectors.toConcurrentMap;
import static java.util.stream.Collectors.toMap;
/**
* stream操作测试
* **
*
* @author: Yuezejian Created in 2020/9/30 上午10:47
* @modified By:
*/
public class TestStreamOperation {
public static final Snowflake snowflake = new Snowflake(12,10);
public static final int COUNT = 10;
long sum = IntStream.of(1,2,3,4,6,7,8,9).filter(e -> e < 5).count();
IntSupplier supplier = () -> 1 ;
Supplier supplier1 = () -> new HashMap<>() ;
public ConcurrentHashMap<String,Long> getList() {
return LongStream.rangeClosed(1,COUNT)
.boxed()
.collect(toConcurrentMap(i -> UUID.randomUUID().toString(), identity(),
(o1,o2) -> o1,ConcurrentHashMap::new));
}
public Map<String,Integer> getList1(List<Integer> list){
return list.stream()
.collect(toMap(i -> snowflake.nextIdStr(), identity(),
(o1,o2) -> o1,HashMap::new));
}
public static void main(String[] args) {
List<Integer> list = Lists.newArrayList();
list = IntStream.builder().add(5).add(4).add(3).add(2).add(1).build().boxed().collect(Collectors.toList());
TestStreamOperation test = new TestStreamOperation();
Map<String,Integer> map = test.getList1(list);
map.entrySet().forEach( i -> {
System.out.println(i.getKey()+ "_"+i.getValue());
});
ConcurrentHashMap<String,Long> map1 = test.getList();
map1.entrySet().forEach(i -> {
System.out.println(i.getKey() +"_"+ i.getValue());
});
System.out.println();
}
}
import com.fasterxml.jackson.databind.ser.Serializers;
import com.tjxskj.taidacity.tools.BaseTest;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.stream.IntStream;
/**
* 用来管理计数器的线程安全类
* 说明：测试结果说明，多线程并发下，AtomicLong的确可以保证线程安全
* **
*
* @author: Yuezejian Created in 2020/9/28 下午5:04
* @modified By:
*/
public class AutomicLongTest extends BaseTest {
private final AtomicLong count = new AtomicLong(0);
public static void main(String[] args) {
AutomicLongTest automicLongTest = new AutomicLongTest();
IntStream.rangeClosed(1,20).parallel().forEach( i -> {
automicLongTest.add();
});
System.out.println(automicLongTest.count);
}
public void add () {
count.incrementAndGet();
log.info("这是第 {} 此进行+1操作",count);
}
//
//7:23:02.382 logback [ForkJoinPool.commonPool-worker-3] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 8 此进行+1操作
//17:23:02.382 logback [ForkJoinPool.commonPool-worker-5] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 8 此进行+1操作
//17:23:02.382 logback [main] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 8 此进行+1操作
//17:23:02.382 logback [ForkJoinPool.commonPool-worker-2] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 8 此进行+1操作
//17:23:02.382 logback [ForkJoinPool.commonPool-worker-1] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 8 此进行+1操作
//17:23:02.382 logback [ForkJoinPool.commonPool-worker-4] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 8 此进行+1操作
//17:23:02.382 logback [ForkJoinPool.commonPool-worker-6] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 8 此进行+1操作
//17:23:02.382 logback [ForkJoinPool.commonPool-worker-7] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 8 此进行+1操作
//17:23:02.388 logback [main] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 10 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-6] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 10 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-7] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 11 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-1] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 12 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-3] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 13 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-1] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 14 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-7] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 15 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-4] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 16 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-2] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 17 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-5] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 18 此进行+1操作
//17:23:02.388 logback [ForkJoinPool.commonPool-worker-4] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 20 此进行+1操作
//17:23:02.388 logback [main] INFO c.t.t.secondchapter.AutomicLongTest - 这是第 20 此进行+1操作
//20
}
装箱和拆箱
public ConcurrentHashMap<String,Long> getList() {
return LongStream.rangeClosed(1,10)
.boxed()
.collect(Collectors.toConcurrentMap(i -> UUID.randomUUID().toString(), identity(),
(o1,o2) -> o1,ConcurrentHashMap::new));
}
public void test() {
//LongStream返回的是一个long类型的流
//List<Long> list = Lists.newArrayLise<>();
long[] lrr = LongStream.rangeClosed(1,10).toArray();
List<Long> list = Lists.newArrayList();
List<Long> list1 = new ArrayList<>(128);
list1 = Arrays.asList(19L,11L);
}
标签：java,worker,ForkJoinPool,偷看,笔记,util,请勿,import,commonPool 来源： https://blog.csdn.net/weixin_42994251/article/details/108976167