04-经典排序案例

实现一个快速排序  将接口对象作为类属性

//: Compare.java

// Interface for sorting callback:

package c08;



interface Compare {

    boolean lessThan(Object lhs, Object rhs);



    boolean lessThanOrEqual(Object lhs, Object rhs);

} // /:~

 

 

排序的实现：

//: SortVector.java

// A generic sorting vector

package c08;



import java.util.*;



public class SortVector extends Vector {

    private Compare compare; // To hold the callback



    public SortVector(Compare comp) { compare = comp; } public void sort() {

        quickSort(0, size() - 1);

    }

    //  4 5

    private void quickSort(int left, int right) {

        if (right > left) {

            Object o1 = elementAt(right);

            int i = left - 1; //3

            int j = right;  //5

            while (true) {

                while (compare.lessThan(elementAt(++i), o1))

                    ;

                while (j > 0)

                    if (compare.lessThanOrEqual(elementAt(--j), o1))



                        break; // out of while

                if (i >= j)

                    break;

                swap(i, j);

            }

            swap(i, right);

            quickSort(left, i - 1);

            quickSort(i + 1, right);

        }

    }

    /**

     * 数据交换位置

     * @param loc1

     * @param loc2

     */

    private void swap(int loc1, int loc2) {

        Object tmp = elementAt(loc1);  //获取loc1位置的数据

        setElementAt(elementAt(loc2), loc1);  //将loc2位置的数据放置在loc1上

        setElementAt(tmp, loc2); //将原loc1上的数据放在loc2上

    }

} // /:~

 

测试案例（需要实现排序的具体规则）

//: StringSortTest.java

// Testing the generic sorting Vector

package c08;



import java.util.*;



public class StringSortTest {

    static class StringCompare implements Compare {

        public boolean lessThan(Object l, Object r) {

            return ((String) l).toLowerCase().compareTo(

                    ((String) r).toLowerCase()) < 0;

        }



        public boolean lessThanOrEqual(Object l, Object r) {

            return ((String) l).toLowerCase().compareTo(

                    ((String) r).toLowerCase()) <= 0;

        }

    }



    public static void main(String[] args) {

        SortVector sv = new SortVector(new StringCompare());

        sv.addElement("d");

        sv.addElement("A");

        sv.addElement("C");

        sv.addElement("c");

        sv.addElement("b");

        sv.addElement("B");

        sv.addElement("D");

        sv.addElement("a");

        sv.sort();

        Enumeration e = sv.elements();

        while (e.hasMoreElements())



            System.out.println(e.nextElement());

    }

} // /:~

 

 

可以通过匿名内部类来实现：

//: StrSortVector.java

// Automatically sorted Vector that

// accepts and produces only Strings

package c08;



import java.util.*;



public class StrSortVector {

    private SortVector v = new SortVector(

    // Anonymous inner class:

            new Compare() {

                public boolean lessThan(Object l, Object r) {

                    return ((String) l).toLowerCase().compareTo(

                            ((String) r).toLowerCase()) < 0;

                }



                public boolean lessThanOrEqual(Object l, Object r) {

                    return ((String) l).toLowerCase().compareTo(

                            ((String) r).toLowerCase()) <= 0;

                }

            });

    private boolean sorted = false; //增加新的元素以后需要重新排序



    public void addElement(String s) {

        v.addElement(s);

        sorted = false;

    }



    public String elementAt(int index) {

        if (!sorted) {

            v.sort();



            sorted = true;

        }

        return (String) v.elementAt(index);

    }



    public Enumeration elements() {

        if (!sorted) {

            v.sort();

            sorted = true;

        }

        return v.elements();

    }



    // Test it:

    public static void main(String[] args) {

        StrSortVector sv = new StrSortVector();

        sv.addElement("d");

        sv.addElement("A");

        sv.addElement("C");

        sv.addElement("c");

        sv.addElement("b");

        sv.addElement("B");

        sv.addElement("D");

        sv.addElement("a"); 

         

        

        Enumeration e = sv.elements();

        while (e.hasMoreElements())

            System.out.println(e.nextElement());

    }

} // /:~