常见Map 及 ArrayList 是否有序总结-白红宇

常见Map 及 ArrayList 是否有序总结

阅读量：4053 次

发布时间：2019-05-25

本文共 3349 字，大约阅读时间需要 11 分钟。

说明：此处的排序是指：

1：往集合中插入元素的顺序与遍历元素的顺序的关系；

2：往对象中插入元素否会根据元素的大小排序

              
public
class
MapSortTest { 
    
public
static
void
main(String[] args) { 
        
        
System.out.println(
"放入顺序为：a:aaa c:ccc b:bbb d:ddd "
);
        
System.out.println(
"HashMap 排序测试"
);
        
Map map = 
new
HashMap(); 
        
map.put(
"a"
, 
"aaa"
);  
        
map.put(
"c"
, 
"ccc"
);
        
map.put(
"b"
, 
"bbb"
); 
        
map.put(
"d"
, 
"ddd"
); 
        
Iterator iterator = map.keySet().iterator(); 
        
while
(iterator.hasNext()) { 
            
Object key = iterator.next(); 
            
System.out.println(
"key:"
+key+
"         value:"
+ map.get(key)); 
        
} 
        
System.out.println(
"HashMap 进出无次序 ； key大小无次序 "
);
        
System.out.println(
"***********************************************************"
);
        
        
        
System.out.println(
"Hashtable 排序测试"
);       
        
Hashtable tab = 
new
Hashtable(); 
        
tab.put(
"a"
, 
"aaa"
); 
        
tab.put(
"c"
, 
"ccc"
);
        
tab.put(
"b"
, 
"bbb"
);  
        
tab.put(
"d"
, 
"ddd"
); 
        
Iterator iterator_1 = tab.keySet().iterator(); 
        
while
(iterator_1.hasNext()) { 
            
Object key = iterator_1.next(); 
            
System.out.println(
"key :"
+key+
"             value:"
+ tab.get(key)); 
        
} 
        
System.out.println(
"Hashtable 进出无次序 ； key大小无次序 "
);
        
System.out.println(
"***********************************************************"
);
        
        
System.out.println(
"TreeMap 排序测试"
);             
        
TreeMap tmp = 
new
TreeMap(); 
        
tmp.put(
"a"
, 
"aaa"
); 
        
tmp.put(
"c"
, 
"ccc"
); 
        
tmp.put(
"b"
, 
"bbb"
); 
        
tmp.put(
"d"
, 
"ddd"
); 
        
Iterator iterator_2 = tmp.keySet().iterator(); 
        
while
(iterator_2.hasNext()) { 
            
Object key = iterator_2.next(); 
            
System.out.println(
"key:"
+key+
"          value:"
+ tmp.get(key)); 
        
} 
        
System.out.println(
"TreeMap 进出无次序 ； key大小从小到大 "
);
        
System.out.println(
"***********************************************************"
);
        
        
System.out.println(
"LinkedHashMap 排序测试"
);               
        
LinkedHashMap linkedHashMap = 
new
LinkedHashMap(); 
        
linkedHashMap.put(
"a"
, 
"aaa"
); 
        
linkedHashMap.put(
"c"
, 
"ccc"
); 
        
linkedHashMap.put(
"b"
, 
"bbb"
); 
        
linkedHashMap.put(
"d"
, 
"ddd"
); 
        
Iterator iterator2 = linkedHashMap.keySet().iterator(); 
        
while
(iterator2.hasNext()) { 
            
Object key = iterator2.next(); 
            
System.out.println(
"key:"
+key+
"          value:"
+ linkedHashMap.get(key)); 
        
}       
        
System.out.println(
"LinkedHashMap 先进先出； key大小无次序 "
);
        
System.out.println();
        
        
System.out.println(
"ArrayList 排序测试"
);
        
System.out.println(
"放入顺序为：aaa ccc bbb ddd"
);
        
ArrayList arrayList=
new
ArrayList(); 
        
arrayList.add(
"aaa"
); 
        
arrayList.add(
"ccc"
); 
        
arrayList.add(
"bbb"
); 
        
arrayList.add(
"ddd"
); 
        
System.out.println(
"ArrayList 先进先出；值大小无次序 "
);
//      Collections.sort(arrayList); 
        
for
(
int
i=
0
;i<arrayList.size();i++){ 
            
System.out.println(arrayList.get(i)); 
        
} 
        
System.out.println(
"***********************************************************"
);
    
}
}
       
     

运行结果：

              
放入顺序为：a:aaa c:ccc b:bbb d:ddd 
HashMap 排序测试
key:d         value:ddd
key:b         value:bbb
key:c         value:ccc
key:a         value:aaa
HashMap 进出无次序 ； key大小无次序 
***********************************************************
Hashtable 排序测试
key :b             value:bbb
key :a             value:aaa
key :d             value:ddd
key :c             value:ccc
Hashtable 进出无次序 ； key大小无次序 
***********************************************************
TreeMap 排序测试
key:a          value:aaa
key:b          value:bbb
key:c          value:ccc
key:d          value:ddd
TreeMap 进出无次序 ； key大小从小到大 
***********************************************************
LinkedHashMap 排序测试
key:a          value:aaa
key:c          value:ccc
key:b          value:bbb
key:d          value:ddd
LinkedHashMap 先进先出； key大小无次序 
ArrayList 排序测试
放入顺序为：aaa ccc bbb ddd
LinkedHashMap 先进先出；值大小无次序 
aaa
ccc
bbb
ddd
***********************************************************
       
     