堆中堆溢出，栈溢出实例，永久区溢出

1.堆溢出

main：
public class HeapOOM {
   
  public static void main(String[] args) {
    List<UserBean> users = new ArrayList<UserBean>();
    while (true) {
      users.add(new UserBean());
    }
  }

bean：
public class UserBean {
  String name;
  int age;
}
然后在运行的时候设置jvm参数
-xmx1m -Xms1m -Xmn1m

运行结果：

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
  at java.util.Arrays.copyOf(Unknown Source)
  at java.util.Arrays.copyOf(Unknown Source)
  at java.util.ArrayList.grow(Unknown Source)
  at java.util.ArrayList.ensureExplicitCapacity(Unknown Source)
  at java.util.ArrayList.ensureCapacityInternal(Unknown Source)
  at java.util.ArrayList.add(Unknown Source)
  at oom.HeapOOM.main(HeapOOM.java:21)

2.栈溢出

main：

public static void main(String[] args) {
    Recursion recursion = new Recursion();
    try {
      recursion.recursionself();
    } catch (Throwable e) {
      System.out.println("current value :" + recursion.currentValue);
      throw e;
    }
  }

bean：
public class Recursion {
    public int currentValue = 0;

    public void recursionself() {
        currentValue += 1;
        recursionself();
    }
}

设置参数 -Xss100k
结果：
Exception in thread "main" java.lang.StackOverflowError
  at testbean.Recursion.recursionself(Recursion.java:7)
  at testbean.Recursion.recursionself(Recursion.java:8)
  at testbean.Recursion.recursionself(Recursion.java:8)
  at testbean.Recursion.recursionself(Recursion.java:8)
  at testbean.Recursion.recursionself(Recursion.java:8)
  at testbean.Recursion.recursionself(Recursion.java:8)

　3.永久区溢出：

第三个异常是关于perm的异常内容，我们需要的是设置方法区的大小，实现方式是通过设置-XX:PermSize和-XX:MaxPermSize参数
如果程序加载的类过多，例如tomcatweb容器，就会出现PermGen space异常，如果我将HeapOOM类的运行时的XX:PermSize设置为1M
那么程序就不会执行成功，执行的时候出现如下异常：
Error occurred during initialization of VM
java.lang.OutOfMemoryError: PermGen space
  at sun.misc.Launcher$ExtClassLoader.getExtClassLoader(Unknown Source)
  at sun.misc.Launcher.<init>(Unknown Source)
  at sun.misc.Launcher.<clinit>(Unknown Source)
  at java.lang.ClassLoader.initSystemClassLoader(Unknown Source)
  at java.lang.ClassLoader.getSystemClassLoader(Unknown Source)