ArrayList<String> dirNo = new ArrayList<String>();
dirNo.add("1");
dirNo.add("2");
dirNo.add("3");
dirNo.add("4");
dirNo.add("5");
dirNo.add("6");
dirNo.add("7");
dirNo.add("8");
dirNo.add("9");
dirNo.add("10");
dirNo.add("11");
System.out.println("max : " + Integer.parseInt(Collections.max(dirNo)));
After executing above code, print 9 as output.
But actually max value should be 11.
Why am I getting 9 as max ?
Since your elements are strings, Collections.max()
is returning the value that's the largest lexicographically.
If you wish to compare the strings numerically, you need to use the two-argument version of Collections.max()
and supply an appropriate comparator:
ArrayList<String> dirNo = new ArrayList<String>();
dirNo.add("1");
dirNo.add("2");
dirNo.add("3");
dirNo.add("4");
dirNo.add("5");
dirNo.add("6");
dirNo.add("7");
dirNo.add("8");
dirNo.add("9");
dirNo.add("10");
dirNo.add("11");
Comparator<String> cmp = new Comparator<String>() {
@Override
public int compare(String o1, String o2) {
return Integer.valueOf(o1).compareTo(Integer.valueOf(o2));
}
};
System.out.println("max : " + Collections.max(dirNo, cmp));
You are using a String collection! String comparison is completely different from number comparsion.
String value "2" > "11"
because '2' > '1'
(first character difference)
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