To convert ArrayList to comma-separated String, these are the approaches available in Java.
- Using append() method of StringBuilder
- Using toString() method
- Using Apache Commons StringUtils class
- Using Stream API
- Using join() method of String class
Method 1(Using append() Method of StringBuilder): StringBuilder in java represents a mutable sequence of characters. In the below example, we used StringBuilder’s append() method. The append method is used to concatenate or add a new set of characters in the last position of the existing string.
public StringBuilder append(char a)
Parameter: The method accepts a single parameter a which is the Char value whose string representation is to be appended.
Return Value: The method returns a string object after the append operation is performed.
Method 2(Using toString() method): toString() is an inbuilt method that returns the value given to it in string format. The below code uses the toString() method to convert ArrayList to a String. The method returns the single string on which the replace method is applied and specified characters are replaced (in this case brackets and spaces).
Here, arraylist is an object of the ArrayList class.
Return Value: It returns a string representation of the arraylist
Method 3(Using Apache Commons StringUtils class): Apache Commons library has a StringUtils class that provides utility function for the string. The join method is used to convert ArrayList to comma-separated strings.
Method 4(Using Stream API): Stream API was introduced in Java 8 and is used to process collections of objects. The joining() method of Collectors Class, in Java, is used to join various elements of a character or string array into a single string object.
Method 5(Using String join() method: We can convert ArrayList to comma-separated String using StringJoiner which is a class in java.util package which is used to construct a sequence of characters(strings) separated by a delimiter and optionally starting with a supplied prefix and ending with a supplied suffix. The join() method of the String class can be used to construct the same.
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