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brianwaybrianway
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[add] add module java-jvm
1 parent 772c78a commit b024c36

8 files changed

Lines changed: 233 additions & 1 deletion

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‎.gitignore‎

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# Others
2020
bin/
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.myeclipse
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.myeclipse
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.hprof

‎java-jvm/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<artifactId>java-learning</artifactId>
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<groupId>com.brianway.learning.java</groupId>
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<version>1.0-SNAPSHOT</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<artifactId>java-jvm</artifactId>
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</project>

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/DirectMemoryOOM.java‎

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package com.brianway.learning.java.jvm;
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import sun.misc.Unsafe;
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import java.lang.reflect.Field;
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/**
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* Created by brian on 17/3/2.
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* 使用 unsafe 分配本机内存
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* VM Args: -Xmx20M -XX:MaxDirectMemorySize=10M
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*/
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public class DirectMemoryOOM {
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private static final int _1MB = 1024 * 1024;
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public static void main(String[] args) throws Exception {
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Field unsafeField = Unsafe.class.getDeclaredFields()[0];
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unsafeField.setAccessible(true);
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Unsafe unsafe = (Unsafe) unsafeField.get(null);
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while (true) {
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unsafe.allocateMemory(_1MB);
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}
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}
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}
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/*
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TODO 没出现 OOM
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*/

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/HeapOOM.java‎

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package com.brianway.learning.java.jvm;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* Created by brian on 17/3/1.
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* Java 堆内存溢出异常测试
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* VM Args: -Xms20m -Xmx20m -XX:+HeapDumpOnOutOfMemoryError
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* (限制堆大小为 20 MB)
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*/
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public class HeapOOM {
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static class OOMObject {
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}
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public static void main(String[] args) {
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List<OOMObject> list = new ArrayList<>();
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while (true) {
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list.add(new OOMObject());
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}
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}
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}
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/*
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java.lang.OutOfMemoryError: Java heap space
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Dumping heap to java_pid25599.hprof ...
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Heap dump file created [27802397 bytes in 0.106 secs]
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Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
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at java.util.Arrays.copyOf(Arrays.java:3210)
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at java.util.Arrays.copyOf(Arrays.java:3181)
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at java.util.ArrayList.grow(ArrayList.java:261)
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at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:235)
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at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:227)
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at java.util.ArrayList.add(ArrayList.java:458)
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at com.brianway.learning.java.jvm.HeapOOM.main(HeapOOM.java:19)
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at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
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at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
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at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
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at java.lang.reflect.Method.invoke(Method.java:498)
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at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
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Process finished with exit code 1
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*/

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/JavaVMStackOOM.java‎

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package com.brianway.learning.java.jvm;
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/**
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* Created by brian on 17/3/1.
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* 创建线程导致内存溢出异常
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* VM Args: -Xss2M
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*/
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public class JavaVMStackOOM {
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private void dontStop() {
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while (true) {
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}
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}
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public void stackLeakByThread() {
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while (true) {
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Thread thread = new Thread(new Runnable() {
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@Override
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public void run() {
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dontStop();
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}
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});
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thread.start();
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}
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}
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public static void main(String[] args) {
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JavaVMStackOOM oom = new JavaVMStackOOM();
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oom.stackLeakByThread();
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}
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}
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/*
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Java HotSpot(TM) 64-Bit Server VM warning: Exception java.lang.OutOfMemoryError occurred dispatching signal SIGINT to handler- the VM may need to be forcibly terminated
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Exception in thread "main" java.lang.OutOfMemoryError: unable to create new native thread
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at java.lang.Thread.start0(Native Method)
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at java.lang.Thread.start(Thread.java:714)
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at com.brianway.learning.java.jvm.JavaVMStackOOM.stackLeakByThread(JavaVMStackOOM.java:22)
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at com.brianway.learning.java.jvm.JavaVMStackOOM.main(JavaVMStackOOM.java:28)
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at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
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at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
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at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
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at java.lang.reflect.Method.invoke(Method.java:498)
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at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
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*/

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/JavaVMStackSOF.java‎

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package com.brianway.learning.java.jvm;
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/**
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* Created by brian on 17/3/1.
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* 虚拟机栈和本地方法栈 OOM 测试
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* VM Args: -Xss256k
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*/
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public class JavaVMStackSOF {
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private int stackLength = 1;
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public void stackLeak() {
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stackLength++;
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stackLeak();
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}
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public static void main(String[] args) {
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JavaVMStackSOF oom = new JavaVMStackSOF();
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try {
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oom.stackLeak();
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} catch (Throwable e) {
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System.out.println("stack length:" + oom.stackLength);
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throw e;
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}
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}
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}
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/*
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stack length:1862
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Exception in thread "main" java.lang.StackOverflowError
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:12)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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at com.brianway.learning.java.jvm.JavaVMStackSOF.stackLeak(JavaVMStackSOF.java:13)
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.....
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Process finished with exit code 1
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*/

‎java-jvm/src/main/java/com/brianway/learning/java/jvm/RuntimeConstantPoolOOM.java‎

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package com.brianway.learning.java.jvm;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* Created by brian on 17/3/2.
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* 运行时常量池导致的内存溢出异常
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* VM Args: -XX:PermSize=10M -XX:MaxPermSize=10M
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*
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* 这两个配置项在 JDK 1.8 已经不支持了
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*/
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public class RuntimeConstantPoolOOM {
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public static void main(String[] args) {
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testEqual();
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//使用 List 保持着常量引用,避免被 Full GC 回收常量池行为
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List<String> list = new ArrayList<>();
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//10MB 的 PermSize 在 integer 范围内足够产生 OOM 了
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int i = 0;
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while (true) {
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list.add(String.valueOf(i++).intern());
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}
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}
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/**
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* JDK 1.8
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* true
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* false
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* intern()不会再复制实例,只是在常量池中记录首次出现的实例引用
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*/
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private static void testEqual(){
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String str1 = new StringBuilder("计算机").append("软件").toString();
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System.out.println(str1.intern() == str1);// true
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String str2 = new StringBuilder("ja").append("va").toString();
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System.out.println(str2.intern() == str2);// false
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}
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}
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/*
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Java HotSpot(TM) 64-Bit Server VM warning: ignoring option PermSize=10M; support was removed in 8.0
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Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=10M; support was removed in 8.0
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*/

‎pom.xml‎

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<module>java-container</module>
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<module>java-io</module>
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<module>java8</module>
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<module>java-jvm</module>
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</modules>
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<dependencyManagement>

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