快速定位Java 内存OOM的问题

java.lang.StackOverflowError
java.lang.OutOfMemoryError：java heap space
java.lang.OutOfMemoryError：GC overhead limit exceeeded
java.lang.OutOfMemoryError：Direct buffer memory
java.lang.OutOfMemoryError：unable to create new native thread
java.lang.OutOfMemoryError：Metaspace

public class StackOverflowErrorDemo {
  public static void main(String[] args) {
    stackOverflowError();
  }
  /**
   * 栈一般是512K，不断的深度调用，直到栈被撑破
   * Exception in thread "main" java.lang.StackOverflowError
   */
  private static void stackOverflowError() {
    stackOverflowError();
  }
}

Exception in thread "main" java.lang.StackOverflowError
  at com.moxi.interview.study.oom.StackOverflowErrorDemo.stackOverflowError(StackOverflowErrorDemo.java:17)

/**
 * Java堆内存不足
 */
public class JavaHeapSpaceDemo {
  public static void main(String[] args) {
    // 堆空间的大小 -Xms10m -Xmx10m
    // 创建一个 80M的字节数组
    byte [] bytes = new byte[80 * 1024 * 1024];
  }
}

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space

-Xms10m -Xmx10m -XX:+PrintGCDetails -XX:MaxDirectMemorySize=5m

/**
 * GC 回收超时
 * JVM参数配置: -Xms10m -Xmx10m -XX:+PrintGCDetails
 */
public class GCOverheadLimitDemo {
  public static void main(String[] args) {
    int i = 0;
    List<String> list = new ArrayList<>();
    try {
      while(true) {
        //1.6时intern()方法发现字符串常量池(存储永久代)没有就复制,物理拷贝
        //1.7时intern()方法发现字符串常量池(存储堆)没有就在保存地址值映射实际堆内存对象
        list.add(String.valueOf(++i).intern());
      }
    } catch (Exception e) {
      System.out.println("***************i:" + i);
      e.printStackTrace();
      throw e;
    } finally {
    }
  }
}

[Full GC (Ergonomics) [PSYoungGen: 2047K->2047K(2560K)] [ParOldGen: 7106K->7106K(7168K)] 9154K->9154K(9728K), [Metaspace: 3504K->3504K(1056768K)], 0.0311093 secs] [Times: user=0.13 sys=0.00, real=0.03 secs] 
[Full GC (Ergonomics) [PSYoungGen: 2047K->0K(2560K)] [ParOldGen: 7136K->667K(7168K)] 9184K->667K(9728K), [Metaspace: 3540K->3540K(1056768K)], 0.0058093 secs] [Times: user=0.00 sys=0.00, real=0.01 secs] 
Heap
 PSYoungGen   total 2560K, used 114K [0x00000000ffd00000, 0x0000000100000000, 0x0000000100000000)
 eden space 2048K, 5% used [0x00000000ffd00000,0x00000000ffd1c878,0x00000000fff00000)
 from space 512K, 0% used [0x00000000fff80000,0x00000000fff80000,0x0000000100000000)
 to  space 512K, 0% used [0x00000000fff00000,0x00000000fff00000,0x00000000fff80000)
 ParOldGen    total 7168K, used 667K [0x00000000ff600000, 0x00000000ffd00000, 0x00000000ffd00000)
 object space 7168K, 9% used [0x00000000ff600000,0x00000000ff6a6ff8,0x00000000ffd00000)
 Metaspace    used 3605K, capacity 4540K, committed 4864K, reserved 1056768K
 class space  used 399K, capacity 428K, committed 512K, reserved 1048576K
Exception in thread "main" java.lang.OutOfMemoryError: GC overhead limit exceeded
  at java.lang.Integer.toString(Integer.java:403)
  at java.lang.String.valueOf(String.java:3099)
  at com.moxi.interview.study.oom.GCOverheadLimitDemo.main(GCOverheadLimitDemo.java:18)

-Xms20m -Xmx20m -XX:+PrintGCDetails -XX:MaxDirectMemorySize=5m

// 只设置了5M的物理内存使用，但是却分配 6M的空间
ByteBuffer bb = ByteBuffer.allocateDirect(6 * 1024 * 1024);

[GC (System.gc()) [PSYoungGen: 2030K->488K(2560K)] 2030K->796K(9728K), 0.0008326 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
[Full GC (System.gc()) [PSYoungGen: 488K->0K(2560K)] [ParOldGen: 308K->712K(7168K)] 796K->712K(9728K), [Metaspace: 3512K->3512K(1056768K)], 0.0052052 secs] [Times: user=0.09 sys=0.00, real=0.00 secs] 
Exception in thread "main" java.lang.OutOfMemoryError: Direct buffer memory
  at java.nio.Bits.reserveMemory(Bits.java:693)
  at java.nio.DirectByteBuffer.<init>(DirectByteBuffer.java:123)
  at java.nio.ByteBuffer.allocateDirect(ByteBuffer.java:311)
  at com.moxi.interview.study.oom.DIrectBufferMemoryDemo.main(DIrectBufferMemoryDemo.java:19)

/**
 * 无法创建更多的线程
 */
public class UnableCreateNewThreadDemo {
  public static void main(String[] args) {
    for (int i = 0; ; i++) {
      System.out.println("************** i = " + i);
      new Thread(() -> {
        try {
          TimeUnit.SECONDS.sleep(Integer.MAX_VALUE);
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
      }, String.valueOf(i)).start();
    }
  }
}

Exception in thread "main" java.lang.OutOfMemoryError: unable to cerate new native thread

-XX:MetaspaceSize=8m -XX:MaxMetaspaceSize=8m

/**
 * 元空间溢出
 *
 */
public class MetaspaceOutOfMemoryDemo {
  // 静态类
  static class OOMTest {
  }
  public static void main(final String[] args) {
    // 模拟计数多少次以后发生异常
    int i =0;
    try {
      while (true) {
        i++;
        // 使用Spring的动态字节码技术
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(OOMTest.class);
        enhancer.setUseCache(false);
        enhancer.setCallback(new MethodInterceptor() {
          @Override
          public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
            return methodProxy.invokeSuper(o, args);
          }
        });
      }
    } catch (Exception e) {
      System.out.println("发生异常的次数:" + i);
      e.printStackTrace();
    } finally {
    }
  }
}

java.lang.OutOfMemoryError:Metaspace