TreeMap

最新推荐文章于 2024-09-26 05:30:00 发布

iteye_1836

最新推荐文章于 2024-09-26 05:30:00 发布

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分类专栏： java.util 文章标签： J#

本文链接：https://blog.youkuaiyun.com/iteye_1836/article/details/81884307

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本文提供了两个Java示例，展示了如何使用TreeMap进行排序。第一个示例通过自定义比较器按账户所有者的姓氏进行排序；第二个示例则介绍了如何通过CollatorComparator类解决中文排序的问题。

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[quote]/*

比较函数类TComp比较两个包含姓和名的字符串。它首先比较姓，具体是这样做的，首先寻找每一个字符串中最后一个空格的下标，然后比较从这个位置开始的每一个元素的子字符串。当两个字符串中姓完全相等时，再比较两个名。这样就形成了先按姓排序，在姓相同的情况下再按名字进行排序的树型映射。

*/
//Use a comparator to sort accounts by last name.
import java.util.*;
//Compare last whole words in two strings.
class TComp implements Comparator{
public int compare(Object a,Object b){
int i,j,k;
String strA,strB;
strA = (String)a;
strB = (String)b;
//find index of beginning of last name
i = strA.lastIndexOf(' ');
j = strB.lastIndexOf(' ');
k = strA.substring(i).compareTo(strB.substring(j));
if(k==0) //last name match,check entire name
return strA.compareTo(strB);
else
return k;
}
//no need to override equals
}
public class TreeMapDemo2{
public static void main(String[] args)
{
//Create a tree map.
TreeMap tm = new TreeMap(new TComp());
//Put elements to the map.
tm.put("Sue Yuan",new Double(17.15));
tm.put("Jiahui Sheng",new Double(78777));
tm.put("Huajiang Chen",new Double(12345.77));
tm.put("Magic Ya",new Double(-99.10));
tm.put("Quanbing Chen",new Double(100.00));
//Get a set of the entries.
Set set = tm.entrySet();
//Get an iterator.
Iterator i = set.iterator();
//Display elements.
while(i.hasNext()){
Map.Entry me = (Map.Entry)i.next();
System.out.println(me.getKey() + ": ");
System.out.println(me.getValue());
}
System.out.println();
//Deposit 1000 into Jiahui Sheng's account
double balance = ((Double)tm.get("Jiahui Sheng")).doubleValue();
tm.put("Jiahui Sheng",new Double(balance + 1000));
System.out.println("Jiahui Sheng's new balance : " + tm.get("Jiahui Sheng"));
}
}

[/quote]

[quote]

public class TreeSort {   

    public static void main(String[] args) {   

        CollatorComparator comparator = new CollatorComparator();   
        TreeMap<String, Object> map = new TreeMap<String, Object>(comparator);   

        for (int i = 0; i < 10; i++) {   
            String s = "" + (int) (Math.random() * 1000);   
            map.put(s, s);   
        }   
        map.put("abcd", "abcd");   
        map.put("Abc", "Abc");   
        map.put("bbb", "bbb");   
        map.put("BBBB", "BBBB");   
        map.put("北京", "北京");   
        map.put("中国", "中国");   
        map.put("上海", "上海");   
        map.put("厦门", "厦门");   
        map.put("香港", "香港");   
        map.put("碑海", "碑海");   
        Collection col = map.values();   
        Iterator it = col.iterator();   
        while (it.hasNext()) {   
            System.out.println(it.next());   
        }   

        // Set set=map.keySet();   

        Iterator its = map.entrySet().iterator();   
        while (its.hasNext()) {   
            // entry的输出结果如key0=value0等   
            Map.Entry entry = (Map.Entry) its.next();   
            Object key = entry.getKey();   
            Object value = entry.getValue();   
            System.out.println(entry);   
            // System.out.println(key);   
            // System.out.println(value);   
        }   
        List list = Collections.synchronizedList(new LinkedList());   

        String s="((2[0-4]\\d|25[0-5]|[01]?\\d\\d?)\\.){3}(2[0-4]\\d|25[0-5]|[01]?\\d\\d?)";   

        System.out.println("122.068.2.0".matches(s));   

    }   
}   

/**  
 * Java中之所以出现偏差，主要是compare方法的问题，所以这里自己实现Comparator接口，  
 * 而国际化的问题，使用Collator类来解决。这里先解决中文问题,代码如下：  
 *   
 *   
 *   
 */  
class CollatorComparator implements Comparator {   

    Collator collator = Collator.getInstance();   

    public int compare(Object element1, Object element2) {   
        CollationKey key1 = collator.getCollationKey(element1.toString());   
        CollationKey key2 = collator.getCollationKey(element2.toString());   
        // return -key1.compareTo(key2); 加负号将逆序   
        return key1.compareTo(key2);   
    }   

}

[/quote]