计算java对象的内存占用

代码引用自：https://blog.csdn.net/antony9118/article/details/54317637  感谢博主分享：

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * This class contains object info generated by ClassIntrospector tool
 */
public class ObjectInfo {
    /** Field name */
    public final String name;
    /** Field type name */
    public final String type;
    /** Field data formatted as string */
    public final String contents;
    /** Field offset from the start of parent object */
    public final int offset;
    /** Memory occupied by this field */
    public final int length;
    /** Offset of the first cell in the array */
    public final int arrayBase;
    /** Size of a cell in the array */
    public final int arrayElementSize;
    /** Memory occupied by underlying array (shallow), if this is array type */
    public final int arraySize;
    /** This object fields */
    public final List<ObjectInfo> children;

    public ObjectInfo(String name, String type, String contents, int offset, int length, int arraySize,
                      int arrayBase, int arrayElementSize) {
        this.name = name;
        this.type = type;
        this.contents = contents;
        this.offset = offset;
        this.length = length;
        this.arraySize = arraySize;
        this.arrayBase = arrayBase;
        this.arrayElementSize = arrayElementSize;
        children = new ArrayList<ObjectInfo>(1);
    }

    public void addChild(final ObjectInfo info) {
        if (info != null) {
            children.add(info);
        }
    }

    /**
     * Get the full amount of memory occupied by a given object. This value may be slightly less than
     * an actual value because we don't worry about memory alignment - possible padding after the last object field.
     *
     * The result is equal to the last field offset + last field length + all array sizes + all child objects deep sizes
     *
     * @return Deep object size
     */
    public long getDeepSize() {
        //return length + arraySize + getUnderlyingSize( arraySize != 0 );
        return addPaddingSize(arraySize + getUnderlyingSize(arraySize != 0));
    }

    long size = 0;

    private long getUnderlyingSize(final boolean isArray) {
        //long size = 0;
        for (final ObjectInfo child : children)
            size += child.arraySize + child.getUnderlyingSize(child.arraySize != 0);
        if (!isArray && !children.isEmpty()) {
            int tempSize = children.get(children.size() - 1).offset + children.get(children.size() - 1).length;
            size += addPaddingSize(tempSize);
        }

        return size;
    }

    private static final class OffsetComparator implements Comparator<ObjectInfo> {
        @Override
        public int compare(final ObjectInfo o1, final ObjectInfo o2) {
            return o1.offset - o2.offset; //safe because offsets are small non-negative numbers
        }
    }

    //sort all children by their offset
    public void sort() {
        Collections.sort(children, new OffsetComparator());
    }

    @Override
    public String toString() {
        final StringBuilder sb = new StringBuilder();
        toStringHelper(sb, 0);
        return sb.toString();
    }

    private void toStringHelper(final StringBuilder sb, final int depth) {
        depth(sb, depth).append("name=").append(name).append(", type=").append(type)
                .append(", contents=").append(contents).append(", offset=").append(offset)
                .append(", length=").append(length);
        if (arraySize > 0) {
            sb.append(", arrayBase=").append(arrayBase);
            sb.append(", arrayElemSize=").append(arrayElementSize);
            sb.append(", arraySize=").append(arraySize);
        }
        for (final ObjectInfo child : children) {
            sb.append('\n');
            child.toStringHelper(sb, depth + 1);
        }
    }

    private StringBuilder depth(final StringBuilder sb, final int depth) {
        for (int i = 0; i < depth; ++i)
            sb.append("\t");
        return sb;
    }

    private long addPaddingSize(long size) {
        if (size % 8 != 0) {
            return (size / 8 + 1) * 8;
        }
        return size;
    }

}

ObjectInfo