我尝试在 Android 中搜索 HashMap,但遇到问题:
考虑这个例子:
HashMap<String, String> meMap=new HashMap<String, String>();
meMap.put("Color1","Red");
meMap.put("Color2","Blue");
meMap.put("Color3","Green");
meMap.put("Color4","White");
现在我想迭代它并获取每种颜色的值并希望显示在“Toast”中。 如何显示?
Iterator myVeryOwnIterator = meMap.keySet().iterator();
while(myVeryOwnIterator.hasNext()) {
String key=(String)myVeryOwnIterator.next();
String value=(String)meMap.get(key);
Toast.makeText(ctx, "Key: "+key+" Value: "+value, Toast.LENGTH_LONG).show();
}
这是一个简单的例子来演示
Map
的用法:
Map<String, String> map = new HashMap<String, String>();
map.put("Color1","Red");
map.put("Color2","Blue");
map.put("Color3","Green");
map.put("Color4","White");
System.out.println(map);
// {Color4=White, Color3=Green, Color1=Red, Color2=Blue}
System.out.println(map.get("Color2")); // Blue
System.out.println(map.keySet());
// [Color4, Color3, Color1, Color2]
for (Map.Entry<String,String> entry : map.entrySet()) {
System.out.printf("%s -> %s%n", entry.getKey(), entry.getValue());
}
// Color4 -> White
// Color3 -> Green
// Color1 -> Red
// Color2 -> Blue
请注意,条目以任意顺序迭代。如果您需要特定的订单,那么您可以考虑例如
LinkedHashMap
Map
界面迭代条目时:
关于不同的
Map
特点:
enum
您可能需要考虑使用
enum
和 EnumMap
而不是 Map<String,String>
。
这没有任何警告!
HashMap<String, String> meMap=new HashMap<String, String>();
meMap.put("Color1","Red");
meMap.put("Color2","Blue");
meMap.put("Color3","Green");
meMap.put("Color4","White");
for (Object o : meMap.keySet()) {
Toast.makeText(getBaseContext(), meMap.get(o.toString()),
Toast.LENGTH_SHORT).show();
}
HashMap<String, String> meMap = new HashMap<String, String>();
meMap.put("Color1", "Red");
meMap.put("Color2", "Blue");
meMap.put("Color3", "Green");
meMap.put("Color4", "White");
Iterator myVeryOwnIterator = meMap.values().iterator();
while(myVeryOwnIterator.hasNext()) {
Toast.makeText(getBaseContext(), myVeryOwnIterator.next(), Toast.LENGTH_SHORT).show();
}
for (Object key : meMap.keySet()) {
String value=(String)meMap.get(key);
Toast.makeText(ctx, "Key: "+key+" Value: "+value, Toast.LENGTH_LONG).show();
}
HashMap<String, String> meMap=new HashMap<String, String>();
meMap.put("Color1","Red");
meMap.put("Color2","Blue");
meMap.put("Color3","Green");
meMap.put("Color4","White");
Iterator iterator = meMap.keySet().iterator();
while( iterator. hasNext() ){
Toast.makeText(getBaseContext(), meMap.get(iterator.next().toString()),
Toast.LENGTH_SHORT).show();
}
这对我有用:
HashMap<String, String> meMap=new HashMap<String, String>();
meMap.put("Color1","Red");
meMap.put("Color2","Blue");
meMap.put("Color3","Green");
meMap.put("Color4","White");
Iterator iterator = meMap.keySet().iterator();
while( iterator. hasNext() )
{
Toast.makeText(getBaseContext(), meMap.get(iterator.next().toString()),
Toast.LENGTH_SHORT).show();
}
Iterator iterator = meMap.keySet().iterator();
while(iterator.hasNext() ){
//get key
String key=(String)iterator.next();
//toast value
Toast.makeText(getBaseContext(),""+(String)meMap.get(key),Toast.LENGTH_SHORT).show();
}
注意:如果您知道密钥,请使用此代码
String value=meMap.get(key);
下面的代码将生成唯一的随机数列表。
int size = 10; // Change according to your need
List<Integer> Lucky = new ArrayList<>();
while(Lucky.size()<size)
{
int r = new Random().nextInt(1000);
if(!Lucky.contains(r)) Lucky.add(r);
}