Java中二维矩阵的表示与转换
 
矩阵在线性代数中有着广泛应用,在科学计算、数据分析处理、线性方程等领域也有着广泛应用,可惜JDK中没有相关的矩阵运算工具包,我自己想实现一个,遗憾的是大学里学的线性代数都忘记完了,书本早已回炉再造了。仅仅实现了点点基础的数据转换层的类实现。现先放到这里,希望有兴趣的博友能继续完善!
 
import java.util.ArrayList;
import java.util.Iterator;
import java.util.logging.Logger;

/**
* 二维结构转换
* File: MatrixStructure.java
* User: leizhimin
* Date: 2008-3-10 16:29:36
*/


public class MatrixStructure {
    private static Logger log = Logger.getLogger(MatrixStructure.class.getName());

    /**
     * 将结果集二维集合数据转换为XML
     *
     * @param columns 列名集合
     * @param result  二维结果集
     * @return 返回格式良好的XML字符串
     */

    public static String listToXML(ArrayList<String> columns, ArrayList<ArrayList> result) {
        StringBuffer sb = new StringBuffer();
        sb.append("<?xml version=\"1.0\"  encoding=\"GB2312\"?>\n")
                .append("<?xml-stylesheet type=\"text/xsl\" href=\"")
                .append("\"?>\n\n");
        sb.append("<rptcontent>\n");
        for (ArrayList al : result) {
            sb.append("\t<row>");
            for (Iterator it_al = al.iterator(), it_c = columns.iterator(); it_al.hasNext() && it_c.hasNext();) {
                String tmp = it_c.next().toString();
                sb.append("\n\t\t<").append(tmp).append(">").append(it_al.next()).append("<").append(tmp).append("/>");
            }
            sb.append("\n\t</row>\n");
        }
        sb.append("</rptcontent>");
        return sb.toString();
    }

    /**
     * 将结果集二维数组数据转换为XML
     *
     * @param columns 列名数组
     * @param result  二维结果集数组
     * @return 返回格式良好的XML字符串
     */

    public static String arrayToXML(Object[] columns, Object[][] result) {
        StringBuffer sb = new StringBuffer();
        sb.append("<?xml version=\"1.0\"  encoding=\"GB2312\"?>\n")
                .append("<?xml-stylesheet type=\"text/xsl\" href=\"")
                .append("\"?>\n\n");
        sb.append("<rptcontent>\n");
        for (Object[] al : result) {
            sb.append("\t<row>");
            for (int i = 0; i < columns.length - 1; i++) {
                sb.append("\n\t\t<").append(columns[i].toString()).append(">").append(al[i].toString()).append("<").append(columns[i].toString()).append("/>");
            }
            sb.append("\n\t</row>\n");
        }
        sb.append("</rptcontent>");
        return sb.toString();
    }

    /**
     * 二维集合转为二维数组
     *
     * @param result 二维集合
     * @return 二维数组
     */

    public static Object[][] listToArray(ArrayList<ArrayList> result) {
        int size = result.size();
        Object obj[][] = new Object[size][];
        if (size == 0) {
            log.info("集合为空,转换数组失败,将返回null!");
            return null;
        }
        for (int i = 0; i < size; i++) {
            obj[i] = result.get(i).toArray();
        }
        return obj;
    }

    /**
     * 将二维数组转为二维ArrayList
     *
     * @param arr 二维数组
     * @return 二维ArrayList
     */

    public static ArrayList<ArrayList> arrayToList(Object[][] arr) {
        ArrayList<ArrayList> all = new ArrayList<ArrayList>();
        for (int i = 0; i < arr.length; i++) {
            all.add(arrayToList(arr[i]));
        }
        return all;
    }

    /**
     * 将一维数组转为List对象
     *
     * @param ar 一维数组
     * @return List对象
     */

    public static ArrayList arrayToList(Object[] ar) {
        ArrayList al = new ArrayList();
        for (Object obj : ar) {
            al.add(obj);
        }
        return al;
    }

    /**
     * 输出二维集合到控制台
     *
     * @param all 二维集合
     */

    public static void listOutputConsole(ArrayList<ArrayList> all) {
        System.out.println("-------输出二维集合到控制台-------");
        for (ArrayList al : all) {
            for (Object a : al) {
                System.out.print(a.toString() + "\t");
            }
            System.out.println();
        }
        System.out.println("\n------------------------");
    }


    /**
     * 将二维数组输出到控制台
     *
     * @param arr 二维数组
     */

    public static void arrrayOutputConsole(Object[][] arr) {
        System.out.println("-------输出二维数组到控制台-------");
        for (Object[] ar : arr) {
            for (Object a : ar) {
                System.out.print(a.toString() + "\t");
            }
            System.out.println();
        }
        System.out.println("\n------------------------");
    }

    /**
     * 将二维数组转为格式美观的字符串
     *
     * @param arr 二维数组
     */

    public static String arrayToString(Object[][] arr) {
        StringBuilder sb = new StringBuilder();
        for (Object[] ar : arr) {
            for (Object a : ar) {
                sb.append(a.toString()).append("\t");
            }
            sb.append("\n");
        }
        return sb.toString();
    }

    /**
     * 将二维集合转为格式美观的字符串
     *
     * @param all 二维集合
     */

    public static String listToString(ArrayList<ArrayList> all) {
        StringBuilder sb = new StringBuilder();
        for (ArrayList al : all) {
            for (Object a : al) {
                sb.append(a.toString()).append("\t");
            }
            sb.append("\n");
        }
        return sb.toString();
    }

    public static void main(String args[]) {
        ArrayList<ArrayList> all = new ArrayList<ArrayList>();
        ArrayList al0 = new ArrayList();
        ArrayList al1 = new ArrayList();
        ArrayList al2 = new ArrayList();

        al0.add("01");
        al0.add("02");
        al1.add("11");
        al1.add("12");
        al2.add("21");
        al2.add("22");

        all.add(al0);
        all.add(al1);
        all.add(al2);

        listOutputConsole(all);

        StringBuffer sb = new StringBuffer();
        ArrayList c = new ArrayList();
        c.add("c1");
        c.add("c2");
        c.add("c3");


        Object[][] obj = listToArray(all);
        arrrayOutputConsole(obj);

        ArrayList<ArrayList> allx = arrayToList(obj);

        String x = arrayToXML(c.toArray(), obj);
        System.out.println(x);
    }
}
 
 
运行结果:
-------输出二维集合到控制台-------
01    02  
11    12  
21    22  

------------------------
-------输出二维数组到控制台-------
01    02  
11    12  
21    22  

------------------------
<?xml version="1.0"  encoding="GB2312"?>
<?xml-stylesheet type="text/xsl" href=""?>

<rptcontent>
    <row>
  <c1>01<c1/>
  <c2>02<c2/>
    </row>
    <row>
  <c1>11<c1/>
  <c2>12<c2/>
    </row>
    <row>
  <c1>21<c1/>
  <c2>22<c2/>
    </row>
</rptcontent>


Process finished with exit code 0