Java – Stream has already been operated upon or closed
编辑教程In Java 8, Stream cannot be reused, once it is consumed or used, the stream will be closed.
1. Example – Stream is closed!
Review the following example, it will throw an IllegalStateException
, saying “stream is closed”.
TestJava8.java
package com.mkyong.java8;
import java.util.Arrays;
import java.util.stream.Stream;
public class TestJava8 {
public static void main(String[] args) {
String[] array = {"a", "b", "c", "d", "e"};
Stream<String> stream = Arrays.stream(array);
// loop a stream
stream.forEach(x -> System.out.println(x));
// reuse it to filter again! throws IllegalStateException
long count = stream.filter(x -> "b".equals(x)).count();
System.out.println(count);
}
}
Output
java.lang.IllegalStateException: stream has already been operated upon or closed
at java.util.stream.AbstractPipeline.
(AbstractPipeline.java:203)
at java.util.stream.ReferencePipeline.
(ReferencePipeline.java:94) at java.util.stream.ReferencePipeline$StatelessOp.
(ReferencePipeline.java:618) at java.util.stream.ReferencePipeline$2.
(ReferencePipeline.java:163) at java.util.stream.ReferencePipeline.filter(ReferencePipeline.java:162) at com.hostingcompass.whois.range.run.TestJava8.main(TestJava8.java:25) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
2. Example – Reuse a stream
For whatever reason, you really want to reuse a Stream, try the following Supplier
solution :
TestJava8.java
package com.mkyong.java8;
import java.util.function.Supplier;
import java.util.stream.Stream;
public class TestJava8 {
public static void main(String[] args) {
String[] array = {"a", "b", "c", "d", "e"};
Supplier<Stream<String>> streamSupplier = () -> Stream.of(array);
//get new stream
streamSupplier.get().forEach(x -> System.out.println(x));
//get another new stream
long count = streamSupplier.get().filter(x -> "b".equals(x)).count();
System.out.println(count);
}
}
Output
a
b
c
d
e
1
Each get()
will return a new stream.
Why?
May I know why you need to reuse a stream, for testing?
References
Mos固件,小电视必刷固件
ES6 教程
Vue.js 教程
JSON 教程
jQuery 教程
HTML 教程
HTML 5 教程
CSS 教程
CSS3 教程
JavaScript 教程
DHTML 教程
JSON在线格式化工具
JS在线运行
JSON解析格式化
jsfiddle中国国内版本
JS代码在线运行
PHP代码在线运行
Java代码在线运行
C语言代码在线运行
C++代码在线运行
Python代码在线运行
Go语言代码在线运行
C#代码在线运行
JSRUN闪电教程系统是国内最先开创的教程维护系统, 所有工程师都可以参与共同维护的闪电教程,让知识的积累变得统一完整、自成体系。
大家可以一起参与进共编,让零散的知识点帮助更多的人。
X
选择支付方式:
立即支付
¥
9.99
无法付款,请点击这里
金额: 0 元
备注:
转账时请填写正确的金额和备注信息,到账由人工处理,可能需要较长时间
备注:
转账时请填写正确的金额和备注信息,到账由人工处理,可能需要较长时间
如有疑问请联系QQ:565830900
正在生成二维码, 此过程可能需要15秒钟