Creating new strings from one string

Split the string using the regex, (?=\\+) where ?= specifies positive lookahead assertion.

Demo:

class Main {
    public static void main(String[] args) {
        String str = "+420354599951 [table] +420354599969 [table] +420354599969 [fax] +420354599969 [mobile]";
        String[] parts = str.split("(?=\\+)");

        // Display each element from the array
        for (String part : parts) {
            System.out.println(part);
        }
    }
}

Output:

+420354599951 [table] 
+420354599969 [table] 
+420354599969 [fax] 
+420354599969 [mobile]

Taking @ElliottFrisch's example one small step further, you can save the Strings in a List using the Java Stream API Collectors as follows:

List<String> numbers = Arrays.stream(str.split("\\]\\s*"))
    .map(x -> String.format("%s]", x))
    .collect(Collectors.toList());

You can use regular expressions for this purpose:

String str = "+420354599951 [table] +420354599969 [table] " +
        "+420354599969 [fax] +420354599969 [mobile]";

String[] arr = Arrays.stream(str
        // replace sequences (0 and more)
        // of whitespace characters
        // after closing square brackets
        // with delimiter characters
        .replaceAll("(])(\\s*)", "$1::::")
        // split this string by
        // delimiter characters
        .split("::::", 0))
        .toArray(String[]::new);

// output in a column
Arrays.stream(arr).forEach(System.out::println);

Output:

+420354599951 [table]
+420354599969 [table]
+420354599969 [fax]
+420354599969 [mobile]

^{See also: How to split a string delimited on if substring can be casted as an int}