排序列表<number>

Collections.sort(li,new Comparator<Number>() {
    @Override
    public int compare(Number o1, Number o2) {
        Double d1 = (o1 == null) ? Double.POSITIVE_INFINITY : o1.doubleValue();
        Double d2 = (o2 == null) ? Double.POSITIVE_INFINITY : o2.doubleValue();
        return  d1.compareTo(d2);
    }
});

Andreas_D's answer

jarnbjo aioobe

Collections.sort(li, new Comparator<Number>() {
    HashSet<Class<? extends Number>> allowedTypes;
    {
        allowedTypes = new HashSet<Class<? extends Number>>();
        allowedTypes.add(Integer.class);
        allowedTypes.add(Double.class);
        allowedTypes.add(Float.class);
        allowedTypes.add(Short.class);
        allowedTypes.add(Byte.class);

    }

    @Override
    public int compare(Number o1, Number o2) {
        Double d1 = (o1 == null) ? Double.POSITIVE_INFINITY : o1.doubleValue();
        Double d2 = (o2 == null) ? Double.POSITIVE_INFINITY : o2.doubleValue();

        if (o1 != null && o2 != null) {
            if (!(allowedTypes.contains(o1.getClass()) && allowedTypes.contains(o2.getClass()))) {
                throw new UnsupportedOperationException("Allowed Types:" + allowedTypes);
            }
        }

        return d1.compareTo(d2);

    }
});

guava's constrained list

List<Number> li = Constraints.constrainedList(new ArrayList<Number>(),
    new Constraint<Number>() {
        HashSet<Class<? extends Number>> allowedTypes;
        {
            allowedTypes = new HashSet<Class<? extends Number>>();
            allowedTypes.add(Integer.class);
            allowedTypes.add(Double.class);
            allowedTypes.add(Float.class);
            allowedTypes.add(Short.class);
            allowedTypes.add(Byte.class);

        }

        @Override
        public Number checkElement(Number arg0) {
            if (arg0 != null) {
                if (allowedTypes.contains(arg0.getClass())) {
                    return arg0;
                }
            }

            throw new IllegalArgumentException("Type Not Allowed");
        }
    }
);

li.add(Double.POSITIVE_INFINITY);
li.add(new Integer(20));
li.add(new Double(12.2));
li.add(new Float(1.2));
li.add(Double.NEGATIVE_INFINITY);
li.add(Float.NEGATIVE_INFINITY);
// li.add(null); //throws exception
// li.add(new BigInteger("22"); //throws exception
li.add(new Integer(20));
System.out.println(li);

Collections.sort(li, new Comparator<Number>() {
    @Override
    public int compare(Number o1, Number o2) {
        Double d1 = o1.doubleValue();
        Double d2 = o2.doubleValue();

        return d1.compareTo(d2);
    }
});

System.out.println(li);

jarnbjo his answer Comparator<Number> Number Double.MAX_VALUE allows us to "see"

new BigDecimal("" + Double.MAX_VALUE).multiply(BigDecimal.TEN)

• Byte Short Integer Long Float Double

• BigInteger

• BigDecimal

• {Double, Float}.NEGATIVE_INFINITY {Double, Float}.POSITIVE_INFINITY

  BigDecimal.doubleValue Double.NEGATIVE_INFINITY Double.POSITIVE_INFINITY

• null

• Comparable

@SuppressWarnings("unchecked")
class NumberComparator implements Comparator<Number> {

    // Special values that are treated as larger than any other.
    private final static List<?> special =
            Arrays.asList(Double.NaN, Float.NaN, null);

    private final static List<?> largest =
            Arrays.asList(Double.POSITIVE_INFINITY, Float.POSITIVE_INFINITY);

    private final static List<?> smallest =
            Arrays.asList(Double.NEGATIVE_INFINITY, Float.NEGATIVE_INFINITY);

    public int compare(Number n1, Number n2) {

        // Handle special cases (including null)
        if (special.contains(n1)) return  1;
        if (special.contains(n2)) return -1;

        if (largest.contains(n1) || smallest.contains(n2)) return  1;
        if (largest.contains(n2) || smallest.contains(n1)) return -1;

        // Promote known values (Byte, Integer, Long, Float, Double and
        // BigInteger) to BigDecimal, as this is the most generic known type.
        BigDecimal bd1 = asBigDecimal(n1);
        BigDecimal bd2 = asBigDecimal(n2);
        if (bd1 != null && bd2 != null)
            return bd1.compareTo(bd2);

        // Handle arbitrary Number-comparisons if o1 and o2 are of same class
        // and implements Comparable.
        if (n1 instanceof Comparable<?> && n2 instanceof Comparable<?>)
            try {
                return ((Comparable) n1).compareTo((Comparable) n2);
            } catch (ClassCastException cce) {
            }

        // If the longValue()s differ between the two numbers, trust these.
        int longCmp = ((Long) n1.longValue()).compareTo(n2.longValue());
        if (longCmp != 0)
            return longCmp;

        // Pray to god that the doubleValue()s differ between the two numbers.
        int doubleCmp = ((Double) n1.doubleValue()).compareTo(n2.doubleValue());
        if (doubleCmp != 0)
            return longCmp;

        // Die a painful death...
        throw new UnsupportedOperationException(
                "Cannot compare " + n1 + " with " + n2);
    }


    // Convert known Numbers to BigDecimal, and the argument n otherwise.
    private BigDecimal asBigDecimal(Number n) {
        if (n instanceof Byte)       return new BigDecimal((Byte) n);
        if (n instanceof Integer)    return new BigDecimal((Integer) n);
        if (n instanceof Short)      return new BigDecimal((Short) n);
        if (n instanceof Long)       return new BigDecimal((Long) n);
        if (n instanceof Float)      return new BigDecimal((Float) n);
        if (n instanceof Double)     return new BigDecimal((Double) n);
        if (n instanceof BigInteger) return new BigDecimal((BigInteger) n);
        if (n instanceof BigDecimal) return (BigDecimal) n;
        return null;
    }
}

ideone.com demo

public class Main {

    public static void main(String[] args) {
        List<Number> li = new ArrayList<Number>();

        // Add an Integer, a Double, a Float, a Short, a Byte and a Long.
        li.add(20);         li.add((short) 17);
        li.add(12.2);       li.add((byte) 100);
        li.add(0.2f);       li.add(19518926L);
        li.add(Double.NaN); li.add(Double.NEGATIVE_INFINITY);
        li.add(Float.NaN);  li.add(Double.POSITIVE_INFINITY);

        // A custom Number
        li.add(new BoolNumber(1));
        li.add(new BoolNumber(0));

        // Add two BigDecimal that are larger than Double.MAX_VALUE.
        BigDecimal largeDec = new BigDecimal("" + Double.MAX_VALUE);
        li.add(largeDec/*.multiply(BigDecimal.TEN)*/);
        li.add(largeDec.multiply(BigDecimal.TEN).multiply(BigDecimal.TEN));

        // Add two BigInteger that are larger than Double.MAX_VALUE.
        BigInteger largeInt = largeDec.toBigInteger().add(BigInteger.ONE);
        li.add(largeInt.multiply(BigInteger.TEN));
        li.add(largeInt.multiply(BigInteger.TEN).multiply(BigInteger.TEN));

        // ...and just for fun...
        li.add(null);

        Collections.shuffle(li);
        Collections.sort(li, new NumberComparator());

        for (Number num : li)
            System.out.println(num);
    }

    static class BoolNumber extends Number {
        boolean b;
        public BoolNumber(int i)    { b = i != 0; }
        public double doubleValue() { return b ?  1d :  0d; }
        public float floatValue()   { return b ?  1f :  0f; }
        public int intValue()       { return b ?   1 :   0; }
        public long longValue()     { return b ?  1L :  0L; }
        public String toString()    { return b ? "1" : "0"; }
    }
}

-Infinity
0
0.2
1
12.2
17
20
100
19518926
1.7976931348623157E+308
17976931348623157000000000...00000000010
1.797693134862315700E+310
179769313486231570000000000000...00000100
Infinity
NaN
null
NaN

null

IllegalArgumentException

Double.NaN 0 Double.POSITIVE_INFINITY Double.NEGATIVE_INFINITY

Collections.sort(li,new Comparator<Number>() {
    @Override
    public int compare(Number o1, Number o2) {

        // null values converted to NaN by convention
        Double d1= (o1 == null) ? Double.NaN : o1.doubleValue();
        Double d2= (o2 == null) ? Double.NaN : o2.doubleValue();

        return  d1.compareTo(d2);
    }
});

Set<Double> doubles = new TreeSet<Double>();
doubles.add(0.);
// doubles.add(null);   // uncommenting will lead to an exception!
doubles.add(Double.NaN);
doubles.add(Double.POSITIVE_INFINITY);
doubles.add(Double.NEGATIVE_INFINITY);

for (Double d:doubles) System.out.println(d);

-Infinity
0.0
Infinity
NaN

package drawFramePackage;

import java.awt.geom.AffineTransform;
import java.util.ArrayList;
import java.util.ListIterator;
import java.util.Random;

public class QuicksortAlgorithm {
    ArrayList<AffineTransform> affs;
    ListIterator<AffineTransform> li;
    Integer count, count2;

    /**
     * @param args
     */
    public static void main(String[] args) {
        new QuicksortAlgorithm();
    }

    public QuicksortAlgorithm(){
        count = new Integer(0);
        count2 = new Integer(1);
        affs = new ArrayList<AffineTransform>();

        for (int i = 0; i <= 128; i++) {
            affs.add(new AffineTransform(1, 0, 0, 1, new Random().nextInt(1024), 0));
        }

        affs = arrangeNumbers(affs);
        printNumbers();
    }

    public ArrayList<AffineTransform> arrangeNumbers(ArrayList<AffineTransform> list) {
        while (list.size() > 1 && count != list.size() - 1) {
            if (list.get(count2).getTranslateX() > list.get(count).getTranslateX()) {
                list.add(count, list.get(count2));
                list.remove(count2 + 1);
            }

            if (count2 == list.size() - 1) {
                count++;
                count2 = count + 1;
            } else {
                count2++;
            }
        }
        return list;
    }

    public void printNumbers(){
        li = affs.listIterator();

        while (li.hasNext()) {
            System.out.println(li.next());
        }
    }
}