Java如何转换List<Object[]> 变成一个字符串[]

Question

I found a lot of ways to convert List< Object > to String[] but it did't work for List< Object[] > . I'm getting error:

java.lang.RuntimeException: java.lang.ClassCastException:
[Ljava.lang.String; cannot be cast to java.lang.String

Code:

public String[] listToArray(List<Object[]> inputList) {
        String[] outputArray = new String[inputList.size()];
        int index = 0;
        for(Object obj : inputList) {
            outputArray[index] = (String) obj;
            index++;
        }
        return outputArray;
    }

Answer 1

Here are the changes I have done to your code to overcome the class cast exception and other possible exceptions which may occur. Your list contains object[] and not Object. Hence the casting to String is throwing error. You can avoid it by iterating it at 2 levels, one for every object[] in list and then every object in object[]. As your List is of Object[] type your code to initialize String[] of list size is not correct under all circumstances, you may end up with Array index out of bounds exception, hence I am adding every string to list and then convert the list to array at last step.

 public static String[] listToArray(List<Object[]> inputList) {
        List<String> outputList = new ArrayList<String>();
        for(Object[] obj : inputList) {
            for(Object obj1 : obj)
            {
                outputList.add((String) obj1);
            }
        }
        return outputList.toArray(new String[outputList.size()]);
    }