how to create a string from string array or arraylist?

问题

how can i extract all the elements in a string [] or arraylist and combine all the words with proper formating(with a single space) between them and store in a array..

String[] a = {"Java", "is", "cool"};

Output: Java is cool.

回答1:

Use a StringBuilder.

String[] strings = {"Java", "is", "cool"};
StringBuilder builder = new StringBuilder();

for (String string : strings) {
    if (builder.length() > 0) {
        builder.append(" ");
    }
    builder.append(string);
}

String string = builder.toString();
System.out.println(string); // Java is cool

Or use Apache Commons Lang StringUtils#join().

String[] strings = {"Java", "is", "cool"};
String string = StringUtils.join(strings, ' ');
System.out.println(string); // Java is cool

Or use Java8's Arrays#stream().

String[] strings = {"Java", "is", "cool"};
String string = Arrays.stream(strings).collect(Collectors.joining(" "));
System.out.println(string); // Java is cool

回答2:

My recommendation would be to use org.apache.commons.lang.StringUtils:

org.apache.commons.lang.StringUtils.join(a, " ");

来源：https://stackoverflow.com/questions/5925420/how-to-create-a-string-from-string-array-or-arraylist