Map<String, String> map ;
List<Map<String, String>> list = new ArrayList<Map<String, String>>();
/////OnCreate.............
function1(){
map = new TreeMap<String, String>();
map.put("id", "id");
map.put("amont", "amount");
list.add(map);
System.out.println(list);
}
id = 1,3,5,57,80
的输入值金额的输入值= 100,500,200,10,10000
无法按金额的升序对列表进行排序。它仍按插入顺序显示。
我该如何解决这个问题?我感谢任何帮助。提前谢谢。
预期产出:金额升序:
amt=10 id=4
amt=100 id=1
amt=200 id=3
amt=500 id=2
amt=10000 id=5
答案 0 :(得分:2)
假设这是你的输入
Map<String, String> map ;
List<Map<String, String>> list = new ArrayList<Map<String, String>>();
map = new TreeMap<String, String>();
map.put("id","1");
map.put("amount","100");
list.add(map);
map = new TreeMap<String, String>();
map.put("id","2");
map.put("amount","500");
list.add(map);
map = new TreeMap<String, String>();
map.put("id","3");
map.put("amount","200");
list.add(map);
map = new TreeMap<String, String>();
map.put("id","4");
map.put("amount","10");
list.add(map);
map = new TreeMap<String, String>();
map.put("id","5");
map.put("amount","10000");
list.add(map);
这是您的分类代码
Collections.sort(list, new Comparator<Map<String, String>>() {
@Override
public int compare(Map<String, String> o1, Map<String, String> o2) {
String value1 = o1.get("amount");
String value2 = o2.get("amount");
return Integer.parseInt(value1)-Integer.parseInt(value2);
}
});
for (Map<String, String> map1 : list) {
String id = map1.get("id");
String amount = map1.get("amount");
System.out.println("amount= "+amount + " , " +"id = "+id);
}
<强>输出强>
amount= 10 , id = 4
amount= 100 , id = 1
amount= 200 , id = 3
amount= 500 , id = 2
amount= 10000 , id = 5
<强>更新强>
如果值为十进制,则使用以下代码替换return Integer.parseInt(value1)-Integer.parseInt(value2);
。
return Double.valueOf(value1).compareTo(Double.valueOf(value2));
答案 1 :(得分:1)
使用sort()
例如:
list.add(map);
Collections.sort(list)
System.out.println(list)
现在它将按照其包含的内容类型的升序打印列表。
答案 2 :(得分:1)
答案 3 :(得分:1)
您必须使用自定义Comparator并在Treemap的构造函数中传递它。例如,在比较器之后使用金额进行排序:
请参阅以下链接。它肯定会解决你的问题
http://java2novice.com/java-collections-and-util/treemap/comparator-user-object/
答案 4 :(得分:1)
默认情况下,列表未排序。您需要Collections.sort()方法Comparator。所以看起来你想按amount
排序,你应该像下面这样实现比较器。
Collections.sort(list, new Comparator<Map<String, String>>() {
@Override
public int compare(Map<String, String> o1, Map<String, String> o2) {
String amount1 = o1.get("amount");
String amount2 = o2.get("amount");
return new Integer(amount1).compareTo(new Integer(amount2));
}
});
这是完整的工作副本,
List<Map<String, String>> list = new ArrayList<Map<String, String>>();
Map<String, String> map1 = new TreeMap<String, String>();
map1.put("id", "2");
map1.put("amount", "200");
Map<String, String> map2 = new TreeMap<String, String>();
map2.put("id", "1");
map2.put("amount", "100");
Map<String, String> map3 = new TreeMap<String, String>();
map3.put("id", "3");
map3.put("amount", "300");
list.add(map1);
list.add(map2);
list.add(map3);
Collections.sort(list, new Comparator<Map<String, String>>() {
@Override
public int compare(Map<String, String> o1, Map<String, String> o2) {
String amount1 = o1.get("amount");
String amount2 = o2.get("amount");
return amount1.compareTo(amount2);
}
});
System.out.println(list);
它应该打印,
[{amount=100, id=1}, {amount=200, id=2}, {amount=300, id=3}]