[java] Convert array of strings into a string in Java

I want the Java code for converting an array of strings into an string.

Use Apache commons StringUtils.join(). It takes an array, as a parameter (and also has overloads for Iterable and Iterator parameters) and calls toString() on each element (if it is not null) to get each elements string representation. Each elements string representation is then joined into one string with a separator in between if one is specified:

String joinedString = StringUtils.join(new Object[]{"a", "b", 1}, "-");
System.out.println(joinedString);

Produces:

a-b-1

String array[]={"one","two"};
String s="";

for(int i=0;i<array.length;i++)
{
  s=s+array[i];
}

System.out.print(s);

From Java 8, the simplest way I think is:

    String[] array = { "cat", "mouse" };
    String delimiter = "";
    String result = String.join(delimiter, array);

This way you can choose an arbitrary delimiter.

Try the Arrays.deepToString method.

Returns a string representation of the "deep contents" of the specified array. If the array contains other arrays as elements, the string representation contains their contents and so on. This method is designed for converting multidimensional arrays to strings

If you know how much elements the array has, a simple way is doing this:

String appendedString = "" + array[0] + "" + array[1] + "" + array[2] + "" + array[3]; 

Following is an example of Array to String conversion.

    public class ArrayToString
    {

        public static void main(String[] args)
        {
            String[] strArray = new String[]{"Java", "PHP", ".NET", "PERL", "C", "COBOL"};

        String newString = Arrays.toString(strArray);

        newString = newString.substring(1, newString.length()-1);

        System.out.println("New New String: " + newString);
    }
}

Try the Arrays.toString overloaded methods.

Or else, try this below generic implementation:

public static void main(String... args) throws Exception {

    String[] array = {"ABC", "XYZ", "PQR"};

    System.out.println(new Test().join(array, ", "));
}

public <T> String join(T[] array, String cement) {
    StringBuilder builder = new StringBuilder();

    if(array == null || array.length == 0) {
        return null;
    }

    for (T t : array) {
        builder.append(t).append(cement);
    }

    builder.delete(builder.length() - cement.length(), builder.length());

    return builder.toString();
}

Use Apache Commons' StringUtils library's join method.

String[] stringArray = {"a","b","c"};
StringUtils.join(stringArray, ",");

You could do this, given an array a of primitive type:

StringBuffer result = new StringBuffer();
for (int i = 0; i < a.length; i++) {
   result.append( a[i] );
   //result.append( optional separator );
}
String mynewstring = result.toString();

You want code which produce string from arrayList,

Iterate through all elements in list and add it to your String result

you can do this in 2 ways: using String as result or StringBuffer/StringBuilder.

Example:

String result = "";
for (String s : list) {
    result += s;
}

...but this isn't good practice because of performance reason. Better is using StringBuffer (threads safe) or StringBuilder which are more appropriate to adding Strings

String[] strings = new String[25000];
for (int i = 0; i < 25000; i++) strings[i] = '1234567';

String result;
result = "";
for (String s : strings) result += s;
//linear +: 5s

result = "";
for (String s : strings) result = result.concat(s);
//linear .concat: 2.5s

result = String.join("", strings);
//Java 8 .join: 3ms

Public String join(String delimiter, String[] s)
{
    int ls = s.length;
    switch (ls)
    {
        case 0: return "";
        case 1: return s[0];
        case 2: return s[0].concat(delimiter).concat(s[1]);
        default:
            int l1 = ls / 2;
            String[] s1 = Arrays.copyOfRange(s, 0, l1); 
            String[] s2 = Arrays.copyOfRange(s, l1, ls); 
            return join(delimiter, s1).concat(delimiter).concat(join(delimiter, s2));
    }
}
result = join("", strings);
// Divide&Conquer join: 7ms

If you don't have the choise but to use Java 6 or 7 then you should use Divide&Conquer join.

I like using Google's Guava Joiner for this, e.g.:

Joiner.on(", ").skipNulls().join("Harry", null, "Ron", "Hermione");

would produce the same String as:

new String("Harry, Ron, Hermione");

ETA: Java 8 has similar support now:

String.join(", ", "Harry", "Ron", "Hermione");

Can't see support for skipping null values, but that's easily worked around.