Concatenating elements in an array to a string

Question

I\'m confused a bit. I couldn\'t find the answer anywhere ;(

I\'ve got an String array:

String[] arr = [\"1\", \"2\", \"3\"];

then

Answer 1

take a look at generic method to print all elements in an array

but in short, the Arrays.toString(arr) is just a easy way of printing the content of a primative array.

Answer 2

Here is a way to do it: Arrays.toString(array).substring(1,(3*array.length-1)).replaceAll(", ","");

Here is a demo class:

package arraytostring.demo;

import java.util.Arrays;

public class Array2String {

        public static void main(String[] args) {

                String[] array = { "1", "2", "3", "4", "5", "6", "7" };
                System.out.println(array2String(array));
                // output is: 1234567
        }

        public static String array2String(String[] array) {

                return Arrays.toString(array).substring(1, (3 * array.length - 1))
                                .replaceAll(", ", "");

        }

}

Scala makes this easier, cleaner and safer:

scala> val a = Array("1", "2", "3")
a: Array[String] = Array(1, 2, 3)

scala> val aString = a.mkString
aString: String = 123

scala> println(aString)
123

Answer 3

Guava has Joiner utility to resolve this issue:

Example:

String joinWithoutSeparator = Joiner.on("").join(1, 2, 3); // returns "123"
String joinWithSeparator = Joiner.on(",").join(1, 2, 3); // returns "1,2,3"

Answer 4

Simple answer:

Arrays.toString(arr);

Answer 5

Arrays.toString(arr);

output is [1,2,3] and you storing it to your string . and printing it so you get output [1,2,3].

If you want to get output 123 try this:

public static void main(String[] args) {
    String[] arr= {"1","2","3"};
    String output ="";
    for(String str: arr)
        output=output+str;
    System.out.println(output);


}

Output:

123

Answer 6

Arrays.toString: (from the API, at least for the Object[] version of it)

public static String toString(Object[] a) {
    if (a == null)
        return "null";
    int iMax = a.length - 1;
    if (iMax == -1)
        return "[]";

    StringBuilder b = new StringBuilder();
    b.append('[');
    for (int i = 0; ; i++) {
        b.append(String.valueOf(a[i]));
        if (i == iMax)
            return b.append(']').toString();
        b.append(", ");
    }
}

So that means it inserts the [ at the start, the ] at the end, and the , between elements.

If you want it without those characters: (StringBuilder is faster than the below, but it can't be the small amount of code)

String str = "";
for (String i:arr)
  str += i;
System.out.println(str);

Side note:

String[] arr[3]= [1,2,3] won't compile.

Presumably you wanted: String[] arr = {"1", "2", "3"};