尽管您不希望使用循环，但我认为您应该使用循环。

String repeatString(String s, int repetitions)
{
    if(repetitions < 0) throw SomeException();

    else if(s == null) return null;

    StringBuilder stringBuilder = new StringBuilder(s.length() * repetitions);

    for(int i = 0; i < repetitions; i++)
        stringBuilder.append(s);

    return stringBuilder.toString();
}

你不使用for循环的理由并不充分。针对你的批评:

Whatever solution you use will almost certainly be longer than this. Using a pre-built function only tucks it under more covers. Someone reading your code will have to figure out what you're doing in that non-for-loop. Given that a for-loop is the idiomatic way to do this, it would be much easier to figure out if you did it with a for loop. Yes someone might add something clever, but by avoiding a for loop you are doing something clever. That's like shooting yourself in the foot intentionally to avoid shooting yourself in the foot by accident. Off-by-one errors are also mind-numbingly easy to catch with a single test. Given that you should be testing your code, an off-by-one error should be easy to fix and catch. And it's worth noting: the code above does not contain an off-by-one error. For loops are equally easy to get right. So don't reuse variables. That's not the for-loop's fault. Again, so does whatever solution you use. And as I noted before; a bug hunter will probably be expecting you to do this with a for loop, so they'll have an easier time finding it if you use a for loop.

如果担心性能问题，只需在循环中使用StringBuilder，并在循环退出时执行. tostring()。见鬼，编写自己的Util类并重用它。最多5行代码。

试试这个吧:

public static char[] myABCs = {'a', 'b', 'c'};
public static int numInput;
static Scanner in = new Scanner(System.in);

public static void main(String[] args) {
    System.out.print("Enter Number of Times to repeat: ");
    numInput = in.nextInt();
    repeatArray(numInput);
}

public static int repeatArray(int y) {
    for (int a = 0; a < y; a++) {
        for (int b = 0; b < myABCs.length; b++) {
            System.out.print(myABCs[b]);                
        }
        System.out.print(" ");
    }
    return y;
}

简单明了的解决方案: 需要Java 8

Collections.nCopies( 3, "abc" ).stream().collect( Collectors.joining() );

public static String repeat(String str, int times) {
    int length = str.length();
    int size = length * times;
    char[] c = new char[size];
    for (int i = 0; i < size; i++) {
        c[i] = str.charAt(i % length);
    }
    return new String(c);
}

如果你使用的是Java <= 7，这是最“简洁”的:

// create a string made up of n copies of string s
String.format("%0" + n + "d", 0).replace("0", s);

在Java 8及以上版本中，有一种更易读的方式:

// create a string made up of n copies of string s
String.join("", Collections.nCopies(n, s));

最后，对于Java 11及以上版本，有一个专门用于此目的的新的repeat (int count)方法(链接)

"abc".repeat(12);

或者，如果您的项目使用java库，则有更多的选项。

对于Apache Commons:

StringUtils.repeat("abc", 12);

谷歌番石榴:

Strings.repeat("abc", 12);