如何进行深拷贝.。。。。

Question

大佬们，我是新手。有一个变量类型是ArrayList<ArrayList<double[]>>，如何进行深拷贝

Answer 1

首先要了解深拷贝，深拷贝：把要复制的对象所引用的对象都复制了一遍，对现在对象的修改不会影响原有的对象。

举个例子：

List list1 = new ArrayList();
List list2 = new ArrayList(list1);
这种方式达不到深拷贝的。这就是浅拷贝：被复制对象的任何变量都含有和原来的对象相同的值，而任何的对其他对象的引用仍然指向原来的对象。对拷贝后的引用的修改，还能影响原来的对象。

List list1 = new ArrayList();
List list2 = new ArrayList();
BeanUtils.copyProperties(list1 , list2);

这样就是深拷贝

copyProperties底层方法

private static void copyProperties(Object source, Object target, @Nullable Class<?> editable, @Nullable String... ignoreProperties) throws BeansException {
    Assert.notNull(source, "Source must not be null");
    Assert.notNull(target, "Target must not be null");
    Class<?> actualEditable = target.getClass();
    if (editable != null) {
        if (!editable.isInstance(target)) {
            throw new IllegalArgumentException("Target class [" + target.getClass().getName() + "] not assignable to Editable class [" + editable.getName() + "]");
        }

        actualEditable = editable;
    }

    PropertyDescriptor[] targetPds = getPropertyDescriptors(actualEditable);
    List<String> ignoreList = ignoreProperties != null ? Arrays.asList(ignoreProperties) : null;
    PropertyDescriptor[] var7 = targetPds;
    int var8 = targetPds.length;

    for(int var9 = 0; var9 < var8; ++var9) {
        PropertyDescriptor targetPd = var7[var9];
        Method writeMethod = targetPd.getWriteMethod();
        if (writeMethod != null && (ignoreList == null || !ignoreList.contains(targetPd.getName()))) {
            PropertyDescriptor sourcePd = getPropertyDescriptor(source.getClass(), targetPd.getName());
            if (sourcePd != null) {
                Method readMethod = sourcePd.getReadMethod();
                if (readMethod != null && ClassUtils.isAssignable(writeMethod.getParameterTypes()[0], readMethod.getReturnType())) {
                    try {
                        if (!Modifier.isPublic(readMethod.getDeclaringClass().getModifiers())) {
                            readMethod.setAccessible(true);
                        }

                        Object value = readMethod.invoke(source);
                        if (!Modifier.isPublic(writeMethod.getDeclaringClass().getModifiers())) {
                            writeMethod.setAccessible(true);
                        }

                        writeMethod.invoke(target, value);
                    } catch (Throwable var15) {
                        throw new FatalBeanException("Could not copy property '" + targetPd.getName() + "' from source to target", var15);
                    }
                }
            }
        }
    }

}