Java For Loop Multiple Lists Simultaneously

Question

If it was up to me, I would loop a Java for loop with multiple lists this way:

for (String s1, s2, s3 : arrayOfString1, arrayOfString2, arrayOfString3)
  {
    System.out.println("arrayOfString1" + s1);
    System.out.println("arrayOfString2" + s2);
    System.out.println("arrayOfString3" + s3);
  }

Sadly, it isn’t up to me, how would I go about looping a for statement with multiple lists?

@xcoder I need to do it simultaneously because all 3 results will later be passed within the same "for loop" ,also note that each s(number) is a list of strings so the loop will put each string in a new line BUT each string of the 3 lists in the same line. — TwoStarII
– TwoStarII, Commented Mar 13, 2015 at 11:34

ch271828n · Accepted Answer · 2015-03-13 11:36:33Z

5

I guess you made the lengths of all the arrays the same. The solution using index is:

for (int i=0;i<arrayOfString1.length();++i) {
    System.out.println("arrayOfString1" + arrayOfString1.get(i));
    System.out.println("arrayOfString2" + arrayOfString2.get(i));
    System.out.println("arrayOfString3" + arrayOfString3.get(i));
}

If you want to use iterator, do as below:(I only print two arrays for example.)

for(Iterator<int> i1=arr1.iterator(),i2=arr2.iterator();i1.hasNext();){
    int val1= i1.next();
    int val2= i2.next();
}

edited Mar 13, 2015 at 11:36

answered Mar 13, 2015 at 11:31

ch271828n

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4 Comments

TwoStarII Over a year ago

I went with the first option but encountered this: Cannot invoke length() on the array type String[], let me quickly convert it and will let you know

TwoStarII Over a year ago

After converting String[] to String the error "The method get(int) is undefined for the type String" is returned, also i is an int, get(i) will return an int, I want to return the strings in the array not an integer or their lengths

ch271828n Over a year ago

If it is a array, use arr.length and arr[i]

TwoStarII Over a year ago

thanks for your time, I didn't know an array would be treated differently for this specific loop given that they contained strings, but now i know.

Björn Kechel · Accepted Answer · 2015-03-13 12:18:26Z

2

try this for lists with different sizes:

int len = arrayOfString1.size();
len = Math.max(len, arrayOfString2.size());
len = Math.max(len, arrayOfString3.size());
for (int i = 0; i < len; i++) {
    if (i < arrayOfString1.size()) System.out.println("arrayOfString1" + arrayOfString1.get(i));
    if (i < arrayOfString2.size()) System.out.println("arrayOfString2" + arrayOfString2.get(i));
    if (i < arrayOfString3.size()) System.out.println("arrayOfString3" + arrayOfString3.get(i));
}

and if you used Arrays, not lists:

int len = arrayOfString1.length;
len = Math.max(len, arrayOfString2.length);
len = Math.max(len, arrayOfString3.length);
for (int i = 0; i < len; i++) {
    if (i < arrayOfString1.length) System.out.println("arrayOfString1" + arrayOfString1[i]);
    if (i < arrayOfString2.length) System.out.println("arrayOfString2" + arrayOfString2[i]);
    if (i < arrayOfString3.length) System.out.println("arrayOfString3" + arrayOfString3[i]);
}

answered Mar 13, 2015 at 12:18

Björn Kechel

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1 Comment

TwoStarII Over a year ago

Thank you, your second method worked!! I'm using an Array. Thank you to all who responded.

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