Java Code Examples for java.util.ArrayList#getClass()

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Example 1

Source File: ArrayListBaseTest.java From jdk-source-analysis with Apache License 2.0

6 votes

/**
 * 通过反射查看 {@link ArrayList} 的内部属性
 */
public void xray(ArrayList list) {
    Class clazz = list.getClass();
    try {
        Field elementData = clazz.getDeclaredField("elementData");
        elementData.setAccessible(true);
        Object[] objects = (Object[]) elementData.get(list);
        Field sizeField = clazz.getDeclaredField("size");
        sizeField.setAccessible(true);

        int size = 0;
        for (int i = 0; i < objects.length; i++) {
            if (Objects.nonNull(objects[i])) {
                ++size;
            }
        }
        System.out.println("length = " + objects.length
                + ", size = " + sizeField.get(list)
                + ", arraySize = " + size);
    } catch (Throwable e) {
        e.printStackTrace();
    }
}