Java: join array of primitives with separator
arrays, java, join, separator
Solution
Here's what I came up with. There are several ways to do this and they depend on the tools you are using.
Using `StringUtils` and `ArrayUtils` from Commons Lang:
int[] arr = new int[] {1, 2, 3, 4, 5, 6, 7};
String result = StringUtils.join(ArrayUtils.toObject(arr), " - ");
You can't just use `StringUtils.join(arr, " - ");` because `StringUtils` doesn't have that overloaded version of method. Though, it has method `StringUtils.join(int[], char)`.
Works at any Java version, from 1.2.
Using Java 8 streams:
Something like this:
int[] arr = new int[] {1, 2, 3, 4, 5, 6, 7};
String result = Arrays.stream(arr)
.mapToObj(String::valueOf)
.collect(Collectors.joining(" - "));
In fact, there are lot of variations to achieve it using streams.
Java 8's method `String.join()` works only with strings, so to use it you still have to convert `int[]` to `String[]`.
String[] sarr = Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new);
String result = String.join(" - ", sarr);
If you're stuck using Java 7 or earlier with no libraries, you could write your own utility method:
public static String myJoin(int[] arr, String separator) {
if (null == arr || 0 == arr.length) return "";
StringBuilder sb = new StringBuilder(256);
sb.append(arr[0]);
//if (arr.length == 1) return sb.toString();
for (int i = 1; i < arr.length; i++) sb.append(separator).append(arr[i]);
return sb.toString();
}
Then you can do:
int[] arr = new int[] {1, 2, 3, 4, 5, 6, 7};
String result = myJoin(arr, " - ");
Problem
Suppose, I have an array: ``` int[] arr = new int[] {1, 2, 3, 4, 5, 6, 7}; ``` And I need to join its elements using separator, for example, `" - "`, so as the result I should get string like this: ``` "1 - 2 - 3 - 4 - 5 - 6 - 7" ``` How could I do this? PS: yes, I know about this and this posts, but its solutions won't work with an array of primitives.