OutOfMemoryError异常 - morris131/morris-book GitHub Wiki
堆存放的是对象，只要不断的创建对象，堆就会溢出。
package com.morris.jvm.oom;
import java.util.ArrayList;
import java.util.List;
/**
* VM args: -Xms 20m -Xmx 20m
*
*/
public class HeapOOM {
public static void main(String[] args) {
List<Object> list = new ArrayList<>();
while(true) {
list.add(new Object());
}
}
}
运行时限制堆的最大值(-Xmx)和最小值(-Xms)。 运行结果如下：
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Arrays.java:3210)
at java.util.Arrays.copyOf(Arrays.java:3181)
at java.util.ArrayList.grow(ArrayList.java:265)
at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:239)
at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:231)
at java.util.ArrayList.add(ArrayList.java:462)
at com.morris.jvm.oom.HeapOOM.main(HeapOOM.java:15)
虚拟机栈这个区域会出现两种异常状况：
- 线程请求的栈深度大于虚拟机所允许的深度，将抛出StackOverflowError 异常；
- 当虚拟机栈扩展时无法申请到足够的内存时会抛出OutOfMemoryError异常。（无法重现）
package com.morris.jvm.oom;
public class StackSOE {
private static void test() {
test();
}
public static void main(String[] args) {
test();
}
}
运行结果如下：
Exception in thread "main" java.lang.StackOverflowError
at com.morris.jvm.oom.StackSOE.test(StackSOE.java:6)
... ...
不断的创建线程就会导致本地方法栈溢出。
package com.morris.jvm.oom;
public class NativeMethodStackOOM {
public static void main(String[] args) {
while(true) {
new Thread(new Runnable() {
@Override
public void run() {
while (true) {
}
}
}).start();
}
}
}
此代码会出现假死，谨慎运行。
字符串常量池方法溢出。
package com.morris.jvm.oom;
import java.util.ArrayList;
import java.util.List;
/**
* VM args: -XX:PermSize=2m -XX:MaxPermSize=2m
*
*/
public class ConstantPoolOOM {
public static void main(String[] args) {
List<String> list = new ArrayList<String>();
int i = 0;
while (true) {
list.add(String.valueOf(i++).intern());
}
}
}
借助CGLib不停的往方法区插入类使方法区出现内存溢出异常。
package com.morris.jvm.oom;
import java.lang.reflect.Method;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
/**
* VM args： -XX:PermSize=2M -XX:MaxPermSize=2M
*/
public class MethodAreaOOM {
public static void main(String[] args) {
while (true) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(OOMObject.class);
enhancer.setUseCache(false);
enhancer.setCallback(new MethodInterceptor() {
@Override
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
return proxy.invokeSuper(obj, args);
}
});
enhancer.create();
}
}
static class OOMObject {
}
}
运行结果如下：
Error occurred during initialization of VM
java.lang.OutOfMemoryError: PermGen space
at java.io.InputStreamReader.<init>(InputStreamReader.java:74)
at java.io.FileReader.<init>(FileReader.java:72)
at sun.misc.MetaIndex.registerDirectory(MetaIndex.java:166)
at sun.misc.Launcher$ExtClassLoader$1.run(Launcher.java:146)
at sun.misc.Launcher$ExtClassLoader$1.run(Launcher.java:142)
at java.security.AccessController.doPrivileged(Native Method)
at sun.misc.Launcher$ExtClassLoader.getExtClassLoader(Launcher.java:141)
at sun.misc.Launcher.<init>(Launcher.java:71)
at sun.misc.Launcher.<clinit>(Launcher.java:57)
at java.lang.ClassLoader.initSystemClassLoader(ClassLoader.java:1489)
at java.lang.ClassLoader.getSystemClassLoader(ClassLoader.java:1474)
package com.morris.jvm.oom;
import java.lang.reflect.Field;
import sun.misc.Unsafe;
/**
* VM args:-Xmx20M -XX:MaxDirectMemorySize=10M
*
*/
@SuppressWarnings("restriction")
public class DirectMemoryOOM {
public static void main(String[] args) throws IllegalArgumentException, IllegalAccessException {
Field field =Unsafe.class.getDeclaredFields()[0];
field.setAccessible(true);
Unsafe unsafe = (Unsafe) field.get(null);
while(true) {
unsafe.allocateMemory(1024*1024);
}
}
}
运行结果如下：
Exception in thread "main" java.lang.OutOfMemoryError
at sun.misc.Unsafe.allocateMemory(Native Method)
at com.morris.jvm.oom.DirectMemoryOOM.main(DirectMemoryOOM.java:20)