如何找到大整数数组列表的最小和最大元素？

Question

How can I find the min and max element of an ArrayList of BigIntegers .

What I've tried is:

import java.math.BigInteger; 
import java.io.*;
import java.util.*;

public class HelloWorld{

     public static void main(String []args){
         BigInteger i1 = new BigInteger("4343345345345");
         BigInteger i2 = new BigInteger("4343453345345345");
         BigInteger i3 = new BigInteger("4343453345");

        List<BigInteger> list = new ArrayList<>();

        list.add(i1);
        list.add(i2);
        list.add(i3);

       BigInteger max = list.stream().max(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);        

        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);

      System.out.println(max.intValue());
      System.out.println(min.intValue());
     }
}

But this gives me the following errors:

HelloWorld.java:20: error: ')' expected
        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);
                                                                                    ^
HelloWorld.java:20: error: ';' expected
        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);
                                                                                     ^
HelloWorld.java:20: error: illegal start of expression
        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);
                                                                                      ^
HelloWorld.java:20: error: ';' expected
        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);
                                                                                       ^
HelloWorld.java:20: error: illegal start of expression
        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);
                                                                                        ^
HelloWorld.java:20: error: ';' expected
        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);
                                                                                                    ^
HelloWorld.java:20: error: not a statement
        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);
                                                                                                     ^
HelloWorld.java:20: error: ';' expected
        BigInteger min = list.stream().min(Comparator.comparing(BigInteger::intValue())).orElseThrow(NoSuchElementExcep::new);

Any other ideas?

Answer 1

Getting min and max does work without comparing intValue s. You should use the natural ordering:

BigInteger max = list.stream().max(BigInteger::compareTo).orElseThrow(NoSuchElementExcep::new);        
BigInteger min = list.stream().min(BigInteger::compareTo).orElseThrow(NoSuchElementExcep::new);

What also doesn't is the way, you're printing the values:

System.out.println(max.intValue());
System.out.println(min.intValue());

You're calling intValue method, but the number exceed the capacity of int (32b). You should rather use:

System.out.println(max);
System.out.println(min);

Answer 2

Simply do

BigInteger max = list.stream().max(BigInteger::compareTo).get();
BigInteger min = list.stream().min(BigInteger::compareTo).get();

Answer 3

The answer is:

import java.io.*;
import java.util.*;


public class HelloWorld{

     public static void main(String []args){
         BigInteger i1 = new BigInteger("4343345345345");
         BigInteger i2 = new BigInteger("4343453345345345");
         BigInteger i3 = new BigInteger("22");

        List<BigInteger> list = new ArrayList<>();

        list.add(i1);
        list.add(i2);
        list.add(i3);


        System.out.println(Collections.min(list, Comparator.naturalOrder()));

     }
}

Answer 4

BigInteger max = list.stream().max(Comparator.comparing(val -> new BigInteger(String.valueOf(val))))
            .orElseThrow(NoSuchElementException::new);
BigInteger min = list.stream().min(Comparator.comparing(val -> new BigInteger(String.valueOf(val))))
            .orElseThrow(NoSuchElementException::new);

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