How make all strings in list one length?

I have a list of names and I need to format it to make all strings same length (add spaces where it needs). Im using java 8 and already got the largest string of list, and I have no idea how to compare other strings to that largest and add spaces where it has to.
My code:

List<String> names = formatNames(abbreviations);
    String max = Collections.max(names, Comparator.comparing(String::length));

private String adjustableString(String format, int number) {
    return IntStream.range(0, number).mapToObj(i -> format).collect(Collectors.joining());
}

You could find the max length of the strings and then align them using String.format:

List<String> names = Arrays.asList("a", "bbb", "12345");
int maxLen = names.stream().mapToInt(String::length).max().getAsInt();

names.stream()
     .map(s -> String.format("%-"+ maxLen+"s", s)) // use "%-5s" to add spaces to the left, "%5s" - to the right
     .forEach(f -> System.out.printf("[%s]%n", f));

Output:

[a    ]
[bbb  ]
[12345]

Update<br/>
Of course, a case of empty list could be handle using orElse(0), but there is another opportunity to chain calculation of optional max length with replacement of values inside the array using List::replaceAll similar to fps' suggestion:

static List<String> padAllToMaxLength(List<String> list) {
    list.stream()
        .mapToInt(String::length)
        .max()
        .ifPresent(max -> doPad(max, list));
    return list;
}

private static void doPad(int spaceCount, List<String> list) {
    System.out.println("doPad: " + spaceCount + ", " + list);
    if (spaceCount > 0) {
        Map<Integer, String> spaces = new HashMap<>();
        list.replaceAll(s -> s.length() == spaceCount ? s
                : s + spaces.computeIfAbsent(spaceCount - s.length(), (x) -> " ".repeat(x)));
        System.out.println("space cache: " + spaces);
    } else {
        System.out.println("nothing to pad");
    }
}

Test

String br = "\n====";
System.out.println("empty list: " + padAllToMaxLength(Collections.emptyList()) + br);
System.out.println("empty values: " + padAllToMaxLength(Arrays.asList("", "", "")) + br);
System.out.println("values: " + padAllToMaxLength(Arrays.asList("", "1", "22", "333", "44", "5", "", "777")) + br);

Output

empty list: []
====
doPad: 0, [, , ]
nothing to pad
empty values: [, , ]
====
doPad: 3, [, 1, 22, 333, 44, 5, , 777]
space cache: {1= , 2=  , 3=   }
values: [   , 1  , 22 , 333, 44 , 5  ,    , 777]
====

You can use String.format() with a format string of "%-99s", where 99 is the max string length:

int maxLen = names.stream().mapToInt(String::length).max().orElse(0);
String format = "%-" + maxLen + "s";
names = names.stream()
             .map(s -> String.format(format, s))
             .collect(Collectors.toList());

The terminal operation should of course be what you need, whether building a new list (like shown here), printing them, concatenating them, ...

Other answers show how to create a new list with the strings formatted. Here's a way to format the strings of the list, in-place:

names.replaceAll(s -> String.format("%-" + max.length() + "s", s));

This assumes that max is the string of the list with max length. It uses List.replaceAll, which accepts a unary operator to transform all the elements of the list.

You can format a string and add spaces where it's needed with String.format:

String.format("%1$"+length+ "s", string);

Just pass the max length and all your strings to the above method.