如何在Java中分割字符串？

Question

I have a group of radio buttons and a group of checkboxes. I want to print out the selected radio buttons/checked boxes. To print out the radio button selected I use

Object table = radio.getValue();
System.out.println(table);

I get the radio button selected. To get which checkboxes have been selected I use the same:

Object columns = check.getValue();
System.out.println(columns);

I get the checkboxes which have been checked but with square brackets surrounding them, eg if I check the boxes

columnA, columnC, columnF

the printed line would look like this:

[columnA, columnC, columnF]

I want to put the strings of the selected checkboxes into my sql query so I have something like this data.executeQuery("Select " + columns + " From " + table);

It works with the table but it doesn't work with the columns .

Answer 1

For this paricular application, you do not need to split a string. You may use

String str = columns.toString(); // "[colummA, colummC, colummF]"
System.out.println(str.substring(1, str.length() - 1));

You may also form a comma-separated string using

StringBuilder sb = new StringBuilder();
for(Object obj : columns) {
    if (sb.length() != 0) sb.append(",");
    sb.append(obj);
}

However, to answer the question:

String is splitted via split(String) method using a Regular Expression syntax. As you have a list of items, converting it to a String and splitting it isnt an effective decision.

Answer 2

columns is an array containing all values of the selected checkboxes. Make sure that the default toString method outputs the items separated by a ","

Answer 3

this is because default

  check.getValue().toString()

called and depending on if its a List or a HashSet and default toString() method of List/HashSet is called which by default appends [] while printing the values so for your case you could either use a collection with a overridden toString() method as per your requirement or just write you custom toString method and call it instead of the default toString Method

here is a sample implementation if it is HashSet

  private String getHashSetString(Set<String> myset){
    StringBuilder sb = new StringBuilder();
    Iterator<String> i = myset.iterator();
    if (! i.hasNext())
        return "";
    for (;;) {
        Long e = i.next();
        sb.append(e);
        if (! i.hasNext())
        return sb.toString();
        sb.append(",");
    }
}

So instead of

  data.executeQuery("Select " + columns + " From " + table);

write

  data.executeQuery("Select " + columns.getHashSetString() + " From " + table);