如何查看应用程序正在使用的当前堆大小？

Question

我想我在 NetBeans 中将堆大小增加到了 1 GB，因为我将配置更改为如下所示：

 netbeans_default_options="-J-Xmx1g ......

在我重新启动 NetBeans 之后，我可以确定我的应用程序现在有 1 GB 空间吗？

有没有办法验证这一点？

原文由 mrblah 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

使用此代码：

 // Get current size of heap in bytes
long heapSize = Runtime.getRuntime().totalMemory();

// Get maximum size of heap in bytes. The heap cannot grow beyond this size.// Any attempt will result in an OutOfMemoryException.
long heapMaxSize = Runtime.getRuntime().maxMemory();

 // Get amount of free memory within the heap in bytes. This size will increase // after garbage collection and decrease as new objects are created.
long heapFreeSize = Runtime.getRuntime().freeMemory();

知道它对我很有用。

原文由 Drewen 发布，翻译遵循 CC BY-SA 2.5 许可协议

Answer 2

public class CheckHeapSize {

    public static void main(String[] args) {
        long heapSize = Runtime.getRuntime().totalMemory();

        // Get maximum size of heap in bytes. The heap cannot grow beyond this size.// Any attempt will result in an OutOfMemoryException.
        long heapMaxSize = Runtime.getRuntime().maxMemory();

         // Get amount of free memory within the heap in bytes. This size will increase // after garbage collection and decrease as new objects are created.
        long heapFreeSize = Runtime.getRuntime().freeMemory();

        System.out.println("heap size: " + formatSize(heapSize));
        System.out.println("heap max size: " + formatSize(heapMaxSize));
        System.out.println("heap free size: " + formatSize(heapFreeSize));

    }
    public static String formatSize(long v) {
        if (v < 1024) return v + " B";
        int z = (63 - Long.numberOfLeadingZeros(v)) / 10;
        return String.format("%.1f %sB", (double)v / (1L << (z*10)), " KMGTPE".charAt(z));
    }
}

原文由 ram kumar 发布，翻译遵循 CC BY-SA 4.0 许可协议