整体描述
前面对运行时数据区描述了很多,其实重点存储数据的是堆和方法区(非堆),所以内存的设计也着重从
这两方面展开(注意这两块区域都是线程共享的)。对于虚拟机栈,本地方法栈,程序计数器都是线程私有的。
(1)一块是非堆区,一块是堆区
(2)堆区分为两大块:一个是Old区,一个是Young区
(3)Young区分为两大块:一个是Survivor区(S0+S1),一块是Eden区
(4)S0和S1一样大,也可以叫From和To
Java Memory Model (JMM待完善)
官网:https://docs.oracle.com/javase/specs/jls/se8/html/jls-17.html#jls-17.4
对象在内存中的分配回收
代码示例
-Xmx50M -Xms50M
堆的OOM
@RestController
public class HeapController {
List<Worker list=new ArrayList<Worker();
@GetMapping("/heap")
public String heap() throws Exception{
while(true){
list.add(new Worker());
}
}
}
运行结果:
方法区的OOM
-XX:MetaspaceSize=50M -XX:MaxMetaspaceSize=50M
(1)asm依赖
<dependency
<groupIdasm</groupId
<artifactIdasm</artifactId
<version3.3.1</version
</dependency
(2)工具类
public class MetaspaceUtil extends ClassLoader {
public static List<Class<? createClasses() {
List<Class<? classes = new ArrayList<Class<?();
for (int i = 0; i < 10000000; ++i) {
ClassWriter cw = new ClassWriter(0);
cw.visit(Opcodes.V1_1, Opcodes.ACC_PUBLIC, "Class" + i, null,
"java/lang/Object", null);
MethodVisitor mw = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init",
"()V", null, null);
mw.visitVarInsn(Opcodes.ALOAD, 0);
mw.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object",
"<init", "()V");
mw.visitInsn(Opcodes.RETURN);
mw.visitMaxs(1, 1);
mw.visitEnd();
MetaspaceUtil test = new MetaspaceUtil();
byte[] code = cw.toByteArray();
Class<? exampleClass = test.defineClass("Class" + i, code, 0, code.length);
classes.add(exampleClass);
}
return classes;
}
}
(3)代码
@RestController
public class NonHeapController {
List<Class<? list=new ArrayList<Class<?();
@GetMapping("/nonheap")
public String heap(){
while(true){
list.addAll(MetaspaceUtil.createClasses());
}
}
}
运行结果:
栈溢出
public class StackOverFlowDemo {
public static long count=0;
public static void method(){
System.out.println(count++);
method();
}
public static void main(String[] args) {
method();
}
}
运行结果:
标签:--,public,method,static,内存,JVM,class From: https://www.cnblogs.com/snail-gao/p/16966812.html