Combining multiple string arrays into one

Question

Basically I have multiple string arrays and I want to combine them.

Not just extend the first array but combine a[0] and b[0] into single line.

like so:

String[] a = {"line1", "line2"};
String[] b = {"line3", "line4"};
String[] c; 
Combine code here
c[0] == "line1line3";
c[1] == "line2line4";

I'm using commons lang v3 if that's any help.

I can combine the 2 arrays with

c = (String[]) ArrayUtils.addAll(a, b);

But that's just makes c = "line1", "line2", "line3", "line4"

Anyone ever done this?

Daniel Fischer · Accepted Answer · 2012-02-25 20:07:24Z

6

If the arrays have the same length, what about

for(int i = 0; i < a.length; ++i){
    c[i] = a[i] + b[i];
}

just concatenating corresponding strings in a loop?

answered Feb 25, 2012 at 20:07

Daniel Fischer

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1 Comment

Jixi Over a year ago

a & b should always be same length although unknown, so yeah that works aslong as i set the length of c. Thanks, so simple :)

Sergey Kalinichenko · Accepted Answer · 2012-02-25 20:25:34Z

6

You can use StringUtils.join from commons lang to "glue" the strings together:

for (int i = 0 ; i != c.length ; i++) {
    c[i] = StrungUtils.join(a[i], b[i]);
}

This might be a bit faster in case that you need to join more than two arrays, but in case of just two arrays it will almost certainly be slower.

edited Feb 25, 2012 at 20:25

answered Feb 25, 2012 at 20:08

Sergey Kalinichenko

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7 Comments

Mob Over a year ago

That's from an external library.

Sergey Kalinichenko Over a year ago

@Mob the OP says he's already using it: "I'm using commons lang v3 if that's any help."

Daniel Fischer Over a year ago

That does the wrong thing, if I understand the OP correctly, that concatenates each array and puts the concatenated strings in the slots of c, but as I understand the OP, (s)he wants to combine corresponding entries of the different arrays.

Ashwinee K Jha Over a year ago

OP wants to join a[0] and b[0] not a[0], a[1].

Jixi Over a year ago

Thanks for this, there's actually 8 arrays so this is definitely helpfull!

|

ZehnVon12 · Accepted Answer · 2012-02-25 20:08:56Z

2

c = new String[a.length];
for (int i=0; i<a.length; i++)
{
  c[i] = a[i] + b[i];
}

answered Feb 25, 2012 at 20:08

ZehnVon12

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Comments

alex · Accepted Answer · 2012-02-25 20:09:12Z

2

you'll have to add handling of invalid indices, but here you go:

String[] c = new String[len];
for( int i = 0; i < len; i++ ){
    c[i] = a[i] + b[i];
}

answered Feb 25, 2012 at 20:09

alex

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