javascript - What are java equivalents to JS push, concat, unshift? - Stack Overflow

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I'm trying to convert the following JS to Java:

serializeSig:function(r,s){
var rBa=r.toByteArraySigned();
var sBa=s.toByteArraySigned();
var sequence=[];
sequence.push(2);
sequence.push(rBa.length);
sequence=sequence.concat(rBa);
sequence.push(2);
sequence.push(sBa.length);
sequence=sequence.concat(sBa);
sequence.unshift(sequence.length);
sequence.unshift(48);
return sequence
}

I think push would translate to add, concat to some kind of addAll, but what is unshift? And of what type would my variables in java be?

I'm trying to convert the following JS to Java:

serializeSig:function(r,s){
var rBa=r.toByteArraySigned();
var sBa=s.toByteArraySigned();
var sequence=[];
sequence.push(2);
sequence.push(rBa.length);
sequence=sequence.concat(rBa);
sequence.push(2);
sequence.push(sBa.length);
sequence=sequence.concat(sBa);
sequence.unshift(sequence.length);
sequence.unshift(48);
return sequence
}

I think push would translate to add, concat to some kind of addAll, but what is unshift? And of what type would my variables in java be?

• java
• javascript

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3 Answers 3

Sorted by: Reset to default 5

myArray.unshift(obj) corresponds to myList.add(0, obj).

A byte array in Java is byte[]. A list of byte arrays would be a List<byte[]>. (That's java.util.List, not java.awt.List, just in case you get the wrong import.)

EDIT: Looks like you are trying to create a byte array, not a list of byte arrays. In that case, you should use a java.nio.ByteBuffer, or possibly a java.io.ByteArrayOutputStream. The latter has to be written to sequentially -- you cannot do the equivalent of an unshift.

This looks like you are trying to use a ByteBuffer to serialize some data.

 public static void serialize(ByteBuffer bb, String r, String s) {
      bb.put(48);
      int start = bb.position();
      bb.put(0); // padding.
      bb.put(2);
      byte[] rBa = r.getBytes();
      bb.put((byte) rBa.length);
      bb.put(rBa);
      byte[] sBa = s.getBytes();
      bb.put((byte) sBa.length);
      bb.put(sBa);
      bb.put(start, (byte) (bb.position() - start - 1));
}

Using an List<Byte> is very inefficient and not supported by the packages which do IO.

You could use an arraylist of Bytes.

List<Byte> sequence = new ArrayList<>();

To add to the end of an arraylist use:

sequence.add(item);

To add to the front use:

sequence.add(0, item);

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