数组列表 <Objects[]> 到要在SQL IN语句中使用的字符串

Question

I am trying to build a string to pass it as an SQL query within the IN statement.

ArrayList<Object[]> arrayList = new ArrayList<Object[]>();

    List<String> strings = new ArrayList<>(arrayList .size());
    for (Object object : arrayList ) {
        strings.add(Objects.toString(object, null));
    }

    System.out.println("askldnlkasdn"+strings);

This still prints out the memory locations instead of the actual string

askldnlkasdn[[Ljava.lang.Object;@7bb11784, [Ljava.lang.Object;@33a10788, [Ljava.lang.Object;@7006c658, [Ljava.lang.Object;@34033bd0, [Ljava.lang.Object;@47fd17e3, [Ljava.lang.Object;@7cdbc5d3, [Ljava.lang.Object;@3aa9e816, [Ljava.lang.Object;@17d99928, [Ljava.lang.Object;@3834d63f, [Ljava.lang.Object;@1ae369b7]

I have also tried out using StringBuilder and StringUtils. But things dont seem to work.

Any inputs as to where the problem is?

Answer 1

您应该在对象中覆盖方法toString

Answer 2

You can use an SQL specific java Array .

try (PreparedStatement stmt = connection.prepareStatement("... IN (?) ...")) {
    Object[] elements = ...
    stmt.setArray(1, connection.createArray("TEXT", elements));
    stmt.executeUpdate();
}

Answer 3

The problem you have is that you are implicitly using the toString() method of the Object elements inside your ArrayList . By default, that method returns the class and address of the Object . You should override the toString() method in every class you will use inside the list so it returns what you want it to.

Answer 4

You can just save it as String , like this code

ArrayList<String> arrayList = new ArrayList<>();

    List<String> strings = new ArrayList<>(arrayList .size());
    for (Object object : arrayList ) {
        strings.add(Objects.toString(object, null));
    }

    System.out.println("askldnlkasdn"+strings);

Or you want it Object for specific purpose?

Answer 5

This is new code that may help,

// Data of Array of Object for test the Code
    Object[] a = new Object[1];
    a[0] = "Hello";
    Object[] b = new Object[1];
    b[0] = "Friend";
    Object[] c = new Object[1];
    c[0] = "This is";
    Object[] d = new Object[1];
    d[0] = "Just Test";

    // The Array List of objects and the data entry
    ArrayList<Object[]> arrayList = new ArrayList<Object[]>();
    arrayList.add(a);
    arrayList.add(b);
    arrayList.add(c);
    arrayList.add(d);

    // New List of strings
    List<String> strings = new ArrayList<>(arrayList .size());


    // The Process of adding the data from array list of objects to the strings
    for(int i = 0; i < arrayList.size(); i++){
        strings.add((String) arrayList.get(i)[0]);
    }

    // Just for print the data to console
    for(int i = 0 ; i < strings.size(); i++){
        System.out.println(strings.get(i));
    }

    System.out.println("askldnlkasdn "+strings.get(0));

I hope that solve the problem, if not please inform me, you can use it for more than one dimensional array .