Can I multiply strings in java to repeat sequences?

Question

I have something like the following:

int i = 3;
String someNum = "123";

I'd like to append i "0"'s to the "someNum" string. Does it have some way I can multiply a string to repeat it like Python does?

So I could just go:

someNum = sumNum + ("0" * 3);

or something similar?

Where, in this case, my final result would be:

"123000".

Answer 1

No, but you can in Scala! (And then compile that and run it using any Java implementation!!!!)

Now, if you want to do it the easy way, use the Apache commons-lang package. Assuming you're using maven, add this dependency to your pom.xml:

    <dependency>
        <groupId>commons-lang</groupId>
        <artifactId>commons-lang</artifactId>
        <version>2.4</version>
    </dependency>

And then use StringUtils.repeat as follows:

import org.apache.commons.lang.StringUtils
...
someNum = sumNum + StringUtils.repeat("0", 3);

Answer 2

No. Java does not have this feature. You'd have to create your String using a StringBuilder, and a loop of some sort.

Answer 3

I don't believe Java natively provides this feature, although it would be nice. I write Perl code occasionally and the x operator in Perl comes in really handy for repeating strings!

However StringUtils in commons-lang provides this feature. The method is called repeat(). Your only other option is to build it manually using a loop.

Answer 4

There's no shortcut for doing this in Java like the example you gave in Python.

You'd have to do this:

for (;i > 0; i--) {
    somenum = somenum + "0";
}

Answer 5

Two ways comes to mind:

int i = 3;
String someNum = "123";

// Way 1:
char[] zeroes1 = new char[i];
Arrays.fill(zeroes1, '0');
String newNum1 = someNum + new String(zeroes1);
System.out.println(newNum1); // 123000

// Way 2:
String zeroes2 = String.format("%0" + i + "d", 0);
String newNum2 = someNum + zeroes2;
System.out.println(newNum2); // 123000

Way 2 can be shortened to:

someNum += String.format("%0" + i + "d", 0);
System.out.println(someNum); // 123000

More about String#format() is available in its API doc and the one of java.util.Formatter.

Answer 6

No, you can't. However you can use this function to repeat a character.

public String repeat(char c, int times){
    StringBuffer b = new StringBuffer();

    for(int i=0;i < times;i++){
        b.append(c);
    }

    return b.toString();
}

Disclaimer: I typed it here. Might have mistakes

Answer 7

With Guava:

Joiner.on("").join(Collections.nCopies(i, someNum));

Answer 8

with Dollar:

String s = "123" + $("0").repeat(3); // 123000