Concatenating Java Arrays in a Loop [duplicate]

Question

I am writing a code for a Signals Software. The summary of logic goes as: users input --> String--> split at white spaces--> ArrayPerWord --> SignalArrayPerArrayPerWord. Output is loop. Up to here my code works well. Only the remaining part left is how to join this loop-output in a sequence. I am searching for concatenating these arrays like String concatenation as:

str=str+str1;

something like:

SignalArrayPerArrayPerWord=SignalArrayPerArrayPerWord   + SignalArrayPerArrayPerWord1;

in other words:

array=array+array1;

I need help at this last step.

Masudul · Accepted Answer · 2014-05-26 05:21:46Z

2

You can use addAll method with List<Integer>. Look at following example.

Integer[] arr={1,2,3};
Integer[] arr2={4,5,9};

List<Integer> res=new ArrayList<>();

res.addAll(Arrays.asList(arr));
res.addAll(Arrays.asList(arr2));

System.out.println(res);

answered May 26, 2014 at 5:21

Masudul

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Community · Accepted Answer · 2017-05-23 12:31:05Z

1

The following will concatenate arrays of same types:

String[] both = ArrayUtils.addAll(first, second);

Its similar to something like this:

ArrayUtils.addAll(["a", "b", "c"], ["1", "2", "3"]) = ["a", "b", "c", "1", "2", "3"]

Further details: doc link

There are multiple ways of concatenating java arrays efficiently, check this stackoverflow post too to find the best example:

stackoverflow post link

edited May 23, 2017 at 12:31

CommunityBot

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answered May 26, 2014 at 5:21

fscore

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2 Comments

Garry Over a year ago

Can I get the result as :{"a", "b", "c", "1", "2", "3"} or I'll have to get it manually?

fscore Over a year ago

If you store the result in a array and print that then you will get what you are looking for.

Ahmet Karakaya · Accepted Answer · 2014-05-26 05:19:52Z

1

you can inspire from the following byte array concatanetion example.

   public static byte[] concatByteArrays(byte[]... arrays) {
      // Determine the length of the result array
      int totalLength = 0;
      for (int i = 0; i < arrays.length; i++) {
         totalLength += arrays[i].length;
      }

      // create the result array
      byte[] result = new byte[totalLength];

      // copy the source arrays into the result array
      int currentIndex = 0;
      for (int i = 0; i < arrays.length; i++) {
         System.arraycopy(arrays[i], 0, result, currentIndex, arrays[i].length);
         currentIndex += arrays[i].length;
      }

      return result;
   }

answered May 26, 2014 at 5:19

Ahmet Karakaya

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Comments

Oleg Gryb · Accepted Answer · 2014-05-26 05:19:59Z

1

ArrayUtils.addAll(array1, array2, ...)

answered May 26, 2014 at 5:19

Oleg Gryb

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Aviad · Accepted Answer · 2014-05-26 05:24:22Z

1

You can use List addAll Method..

List<String> signalArrayPerArrayPerWord = new ArrayList<String>();
List<String> signalArrayPerArrayPerWord1 = new ArrayList<String>();

List<String> concatArray = new ArrayList<String>();

//concat
concatArray.addAll(signalArrayPerArrayPerWord);
concatArray.addAll(signalArrayPerArrayPerWord1);

Hope that helps

answered May 26, 2014 at 5:24

Aviad

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Comments

Inder Sharma · Accepted Answer · 2014-05-26 05:39:06Z

0

Use StringBuilder sb = new StringBuilder();

and in loop use sb.append( "loop element at index" );

answered May 26, 2014 at 5:39

Inder Sharma

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