深入理解java虚拟机(第一篇)

 2019-12-22 10:52  阅读(894)
文章分类:JVM

在eclipse中查看内存溢出的案例:

package main;

    import java.util.ArrayList;
    import java.util.List;

    /**
     * @author 刘卫卫
     * 2018年9月12日下午3:22:49
     */
    public class HeapOOM {

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

在debug标签中设置jvm参数

2019120001384\_1.png

限制java堆的大小为20M,并且不可扩展。这里讲Xms,Xmx(堆的最小值和最小值)都设置为20M即可避免对自动扩展。

对溢出打印的信息:

[GC (Allocation Failure) [PSYoungGen: 7622K->664K(9216K)] 7622K->2782K(19456K), 0.0052667 secs] [Times: user=0.00 sys=0.00, real=0.04 secs] 
    [Full GC (Ergonomics) [PSYoungGen: 8734K->0K(9216K)] [ParOldGen: 9240K->7696K(10240K)] 17974K->7696K(19456K), [Metaspace: 2605K->2605K(1056768K)], 0.0675706 secs] [Times: user=0.13 sys=0.00, real=0.07 secs] 
    [GC (Allocation Failure) [PSYoungGen: 0K->0K(9216K)] 7696K->7696K(19456K), 0.0005580 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 
    [Full GC (Allocation Failure) [PSYoungGen: 0K->0K(9216K)] [ParOldGen: 7696K->7673K(10240K)] 7696K->7673K(19456K), [Metaspace: 2605K->2605K(1056768K)], 0.0313635 secs] [Times: user=0.09 sys=0.00, real=0.03 secs] 
    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:261)
        at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:235)
        at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:227)
        at java.util.ArrayList.add(ArrayList.java:458)
        at main.HeapOOM.main(HeapOOM.java:15)
    Heap
     PSYoungGen      total 9216K, used 241K [0x00000000ff600000, 0x0000000100000000, 0x0000000100000000)
      eden space 8192K, 2% used [0x00000000ff600000,0x00000000ff63c638,0x00000000ffe00000)
      from space 1024K, 0% used [0x00000000fff00000,0x00000000fff00000,0x0000000100000000)
      to   space 1024K, 0% used [0x00000000ffe00000,0x00000000ffe00000,0x00000000fff00000)
     ParOldGen       total 10240K, used 7673K [0x00000000fec00000, 0x00000000ff600000, 0x00000000ff600000)
      object space 10240K, 74% used [0x00000000fec00000,0x00000000ff37e548,0x00000000ff600000)
     Metaspace       used 2637K, capacity 4486K, committed 4864K, reserved 1056768K
      class space    used 280K, capacity 386K, committed 512K, reserved 1048576K

java.lang.OutOfMemoryError: Java heap space

次错误指示内存溢出,而且是堆内存

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