Java虚拟机读书笔记

2.4实战:OutOfMemoryError异常(部分情况代码段

2017-07-31  本文已影响0人  MoscowAug

2.4.1 Java堆溢出

/**
 * VM Args:-Xms20m-Xmx20m-XX:+HeapDumpOnOutOfMemoryError
 */
public class HeapOOM {
    static class OOMObject {
    }

    public static void main(String[] args) {
        List<OOMObject> list = new ArrayList<>();
        while (true) {
            list.add(new OOMObject());
        }
    }
}

运行结果;
java.lang.OutOfMemoryError:Java heap space
Dumping heap to java_pid3404.hprof……
Heap dump file created[22045981 bytes in 0.663 secs]

2.4.2 虚拟机栈和本地方法栈溢出

/**
 * VM Args:-Xss128k *@author zzm
 */
public class JavaVMStackSOF {
    private int stackLength = 1;

    public void stackLeak() {
        stackLength++;
        stackLeak();
    }

    public static void main(String[] args) throws Throwable {
        JavaVMStackSOF oom = new JavaVMStackSOF();
        try {
            oom.stackLeak();
        } catch (Throwable e) {
            System.out.println("stack length:" + oom.stackLength);
            throw e;
        }
    }
}
/**
 * VM Args:-Xss2M(这时候不妨设置大些) *@author zzm
 */
public class JavaVMStackOOM {
    private void dontStop() {
        while (true) {
        }
    }

    public void stackLeakByThread() {
        while (true) {
            Thread thread = new Thread(new Runnable() {
                @Override
                public void run() {
                    dontStop();
                }
            });
            thread.start();
        }
    }

    public static void main(String[] args) throws Throwable {
        JavaVMStackOOM oom = new JavaVMStackOOM();
        oom.stackLeakByThread();
    }
}

2.4.3 方法区和运行时常量池溢出

/**
* 在JDK 1.6及之前的版本中,由 于常量池分配在永久代内,我们可以通过-XX:PermSize和-XX:MaxPermSize限制方法区大 小,从而间接限制其中常量池的容量
 * VM Args:-XX:PermSize=10M-XX:MaxPermSize=10M
 */
public class RuntimeConstantPoolOOM {
    public static void main(String[] args) {
        //使用List保持着常量池引用,避免Full GC回收常量池行
        List<String> list = new ArrayList<>();
        //10MB的PermSize在integer范围内足够产生OOM了
        int i = 0;
        while (true) {
            list.add(String.valueOf(i++).intern());
        }
    }
}  

2.4.4 本机直接内存溢出

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