import java.util.ArrayList; import java.util.Collections; import java.util.List; import java.util.Random; public class IntegersConcat { private final List rndNumbers; private final int size; private final List oneDigit; private final List twoDigit; public static void main(String[] args) { IntegersConcat ic = create(10); ic.separate(); System.out.printf("List: %s%nSmallest number: %s%n", ic, ic.concat()); } private IntegersConcat(List args) { this.rndNumbers = args; this.size = args.size(); this.oneDigit = new ArrayList<>(); this.twoDigit = new ArrayList<>(); } public static IntegersConcat create(int size) { List list = new ArrayList<>(); Random rnd = new Random(); for (int i = 0; i < size; i++) { list.add(rnd.nextInt(99) + 1); } return new IntegersConcat(list); } public void separate() { rndNumbers.forEach((number) -> { if (number / 10 == 0) { oneDigit.add(number); } else { twoDigit.add(number); } }); Collections.sort(oneDigit); Collections.sort(twoDigit); } public String concat() { String result = ""; int i = 0, j = 0; if (this.oneDigit.size() > 0) { while (i < this.oneDigit.size() && j < this.twoDigit.size() && i + j < this.size) { String oneD = String.valueOf(this.oneDigit.get(i)); String twoD = String.valueOf(this.twoDigit.get(j)); if (oneD.charAt(0) < twoD.charAt(0)) { result += oneD; i++; } else if (oneD.charAt(0) == twoD.charAt(0)) { if (oneD.charAt(0) <= twoD.charAt(1)) { result += oneD; i++; } else { result += twoD; j++; } } else { result += twoD; j++; } } for (;i < this.oneDigit.size(); i++) { result += String.valueOf(this.oneDigit.get(i)); } for (;j < this.twoDigit.size(); j++) { result += String.valueOf(this.twoDigit.get(j)); } } else { List sorted = rndNumbers; Collections.sort(sorted); result = sorted.stream().map((number) -> String.valueOf(number)).reduce(result, String::concat); } return result; } @Override public String toString() { String result = ""; result = rndNumbers.stream().map((number) -> number + ", ").reduce(result, String::concat); return result.substring(0, result.length() - 2); } }