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());
    }
} // /:~