归并排序：

package org.rut.util.algorithm.support;

import org.rut.util.algorithm.SortUtil;

/**
 * @author treeroot
 * @since 2006-2-2
 * @version 1.0
 */
public class MergeSort implements SortUtil.Sort{

    /* (non-Javadoc)
     * @see org.rut.util.algorithm.SortUtil.Sort#sort(int[])
     */
    public void sort(int[] data) {
        int[] temp=new int[data.length];
        mergeSort(data,temp,0,data.length-1);
    }
    
    private void mergeSort(int[] data,int[] temp,int l,int r){
        int mid=(l+r)/2;
        if(l==r) return ;
        mergeSort(data,temp,l,mid);
        mergeSort(data,temp,mid+1,r);
        for(int i=l;i<=r;i++){
            temp[i]=data[i];
        }
        int i1=l;
        int i2=mid+1;
        for(int cur=l;cur<=r;cur++){
            if(i1==mid+1)
                data[cur]=temp[i2++];
            else if(i2>r)
                data[cur]=temp[i1++];
            else if(temp[i1]<temp[i2])
                data[cur]=temp[i1++];
            else
                data[cur]=temp[i2++];           
        }
    }

}

改进后的归并排序:

package org.rut.util.algorithm.support;

import org.rut.util.algorithm.SortUtil;

/**
 * @author treeroot
 * @since 2006-2-2
 * @version 1.0
 */
public class ImprovedMergeSort implements SortUtil.Sort {

    private static final int THRESHOLD = 10;

    /*
     * (non-Javadoc)
     *
     * @see org.rut.util.algorithm.SortUtil.Sort#sort(int[])
     */
    public void sort(int[] data) {
        int[] temp=new int[data.length];
        mergeSort(data,temp,0,data.length-1);
    }

    private void mergeSort(int[] data, int[] temp, int l, int r) {
        int i, j, k;
        int mid = (l + r) / 2;
        if (l == r)
            return;
        if ((mid - l) >= THRESHOLD)
            mergeSort(data, temp, l, mid);
        else
            insertSort(data, l, mid - l + 1);
        if ((r - mid) > THRESHOLD)
            mergeSort(data, temp, mid + 1, r);
        else
            insertSort(data, mid + 1, r - mid);

        for (i = l; i <= mid; i++) {
            temp[i] = data[i];
        }
        for (j = 1; j <= r - mid; j++) {
            temp[r - j + 1] = data[j + mid];
        }
        int a = temp[l];
        int b = temp[r];
        for (i = l, j = r, k = l; k <= r; k++) {
            if (a < b) {
                data[k] = temp[i++];
                a = temp[i];
            } else {
                data[k] = temp[j--];
                b = temp[j];
            }
        }
    }

    /**
     * @param data
     * @param l
     * @param i
     */
    private void insertSort(int[] data, int start, int len) {
        for(int i=start+1;i<start+len;i++){
            for(int j=i;(j>start) && data[j]<data[j-1];j--){
                SortUtil.swap(data,j,j-1);
            }
        }
    }

}

堆排序：

package org.rut.util.algorithm.support;

import org.rut.util.algorithm.SortUtil;

/**
 * @author treeroot
 * @since 2006-2-2
 * @version 1.0
 */
public class HeapSort implements SortUtil.Sort{

    /* (non-Javadoc)
     * @see org.rut.util.algorithm.SortUtil.Sort#sort(int[])
     */
    public void sort(int[] data) {
        MaxHeap h=new MaxHeap();
        h.init(data);
        for(int i=0;i<data.length;i++)
            h.remove();
        System.arraycopy(h.queue,1,data,0,data.length);
    }

     private static class MaxHeap{         
        
        void init(int[] data){
            this.queue=new int[data.length+1];
            for(int i=0;i<data.length;i++){
                queue[++size]=data[i];
                fixUp(size);
            }
        }
        
        private int size=0;

        private int[] queue;
                
        public int get() {
            return queue[1];
        }

        public void remove() {
            SortUtil.swap(queue,1,size--);
            fixDown(1);
        }
        //fixdown
        private void fixDown(int k) {
            int j;
            while ((j = k << 1) <= size) {
                if (j < size && queue[j]<queue[j+1])
                    j++;
                if (queue[k]>queue[j]) //不用交换
                    break;
                SortUtil.swap(queue,j,k);
                k = j;
            }
        }
        private void fixUp(int k) {
            while (k > 1) {
                int j = k >> 1;
                if (queue[j]>queue[k])
                    break;
                SortUtil.swap(queue,j,k);
                k = j;
            }
        }

    }

}

SortUtil：

package org.rut.util.algorithm;

import org.rut.util.algorithm.support.BubbleSort;
import org.rut.util.algorithm.support.HeapSort;
import org.rut.util.algorithm.support.ImprovedMergeSort;
import org.rut.util.algorithm.support.ImprovedQuickSort;
import org.rut.util.algorithm.support.InsertSort;
import org.rut.util.algorithm.support.MergeSort;
import org.rut.util.algorithm.support.QuickSort;
import org.rut.util.algorithm.support.SelectionSort;
import org.rut.util.algorithm.support.ShellSort;

/**
 * @author treeroot
 * @since 2006-2-2
 * @version 1.0
 */
public class SortUtil {
    public final static int INSERT = 1;
    public final static int BUBBLE = 2;
    public final static int SELECTION = 3;
    public final static int SHELL = 4;
    public final static int QUICK = 5;
    public final static int IMPROVED_QUICK = 6;
    public final static int MERGE = 7;
    public final static int IMPROVED_MERGE = 8;
    public final static int HEAP = 9;

    public static void sort(int[] data) {
        sort(data, IMPROVED_QUICK);
    }
    private static String[] name={
            "insert", "bubble", "selection", "shell", "quick", "improved_quick", "merge", "improved_merge", "heap"
    };
    
    private static Sort[] impl=new Sort[]{
            new InsertSort(),
            new BubbleSort(),
            new SelectionSort(),
            new ShellSort(),
            new QuickSort(),
            new ImprovedQuickSort(),
            new MergeSort(),
            new ImprovedMergeSort(),
            new HeapSort()
    };

    public static String toString(int algorithm){
        return name[algorithm-1];
    }
    
    public static void sort(int[] data, int algorithm) {
        impl[algorithm-1].sort(data);
    }

    public static interface Sort {
        public void sort(int[] data);
    }

    public static void swap(int[] data, int i, int j) {
        int temp = data[i];
        data[i] = data[j];
        data[j] = temp;
    }
}