How to print all key and values from HashMap in Android?
JavaAndroidKeyHashmapJava Problem Overview
I am very new for Android development, and I am trying to use HashMap in Android sample project. Now, am doing sample project for learn android. I just store keys and values in HashMap, i want to show the keys and their values in EditView. I followed below code in my sample project. But, first key and value only printing in EditView.
Map<String, String> map = new HashMap<String,String>();
map.put("iOS", "100");
map.put("Android", "101");
map.put("Java", "102");
map.put(".Net", "103");
Set keys = map.keySet();
for (Iterator i = keys.iterator(); i.hasNext(); ) {
String key = (String) i.next();
String value = (String) map.get(key);
textview.setText(key + " = " + value);
}
In EditView iOS = 100
is only printing. I want to print all keys and their value in EditText. Can anyone please tell me where i am doing wrong? Thanks in advance.
Java Solutions
Solution 1 - Java
for (Map.Entry<String,String> entry : map.entrySet()) {
String key = entry.getKey();
String value = entry.getValue();
// do stuff
}
Solution 2 - Java
It's because your TextView recieve new text on every iteration and previuos value thrown away. Concatenate strings by StringBuilder and set TextView value after loop. Also you can use this type of loop:
for (Map.Entry<String, String> e : map.entrySet()) {
//to get key
e.getKey();
//and to get value
e.getValue();
}
Solution 3 - Java
You can do it easier with Gson:
Log.i(TAG, "SomeText: " + new Gson().toJson(yourMap));
The result will look like:
I/YOURTAG: SomeText: {"key1":"value1","key2":"value2"}
Solution 4 - Java
First, there are errors in your code, ie. you are missing a semicolon and a closing parenthesis in the for loop.
Then, if you are trying to append values to the view, you should use textview.appendText(), instead of .setText().
There's a similar question here: https://stackoverflow.com/questions/2300169/how-to-change-text-in-android-textview
Solution 5 - Java
HashMap <Integer,Integer> hm = new HashMap<Integer,Integer>();
Set<Integer> keys = hm.keySet(); //get all keys
for(Integer i: keys)
{
System.out.println(hm.get(i));
}
Solution 6 - Java
With Java 8:
map.keySet().forEach(key -> System.out.println(key + "->" + map.get(key)));
Solution 7 - Java
Java 8
map.entrySet().forEach(System.out::println);
Solution 8 - Java
for (String entry : map.keySet()) {
String value = map.get(entry);
System.out.print(entry + "" + value + " ");
// do stuff
}
Solution 9 - Java
String text="";
for (Iterator i = keys.iterator(); i.hasNext()
{
String key = (String) i.next();
String value = (String) map.get(key);
text+=key + " = " + value;
}
textview.setText(text);
Solution 10 - Java
This code is tested and working.
public void dumpMe(Map m) { dumpMe(m, ""); }
private void dumpMe(Map m, String padding) {
Set s = m.keySet();
java.util.Iterator ir = s.iterator();
while (ir.hasNext()) {
String key = (String) ir.next();
Object value = m.get(key);
if (value == null) continue;
if (value instanceof Map) {
System.out.println (padding + key + " = {");
dumpMe((Map)value, padding + " ");
System.out.println(padding + "}");
}
else if (value instanceof String ||
value instanceof Integer ||
value instanceof Double ||
value instanceof Float ||
value instanceof Long ) {
System.out.println(padding + key + " = " + value.toString());
}
else {
System.out.println(padding + key + " = UNKNOWN OBJECT: " + value.toString());
// You could also throw an exception here
}
} // while
} // dumpme
Charles.
Solution 11 - Java
you can use this code:
for (Object variableName: mapName.keySet()){
variableKey += variableName + "\n";
variableValue += mapName.get(variableName) + "\n";
}
System.out.println(variableKey + variableValue);
this code will make sure that all the keys are stored in a variable and then printed!
Solution 12 - Java
public void dumpMe(Map m) { dumpMe(m, ""); }
private void dumpMe(Map m, String padding)
{
Set s = m.keySet();
java.util.Iterator ir = s.iterator();
while (ir.hasNext())
{
String key = (String) ir.next();
AttributeValue value = (AttributeValue)m.get(key);
if (value == null)
continue;
if (value.getM() != null)
{
System.out.println (padding + key + " = {");
dumpMe((Map)value, padding + " ");
System.out.println(padding + "}");
}
else if (value.getS() != null ||
value.getN() != null )
{
System.out.println(padding + key + " = " + value.toString());
}
else
{
System.out.println(padding + key + " = UNKNOWN OBJECT: " + value.toString());
// You could also throw an exception here
}
} // while
}
//This code worked for me.
Solution 13 - Java
To print all keys:
myMap.keys().toList().joinToString()
To print all entries:
myMap.map { "${it.key} :: ${it.value}" }.toList().joinToString()
Solution 14 - Java
For everyone who clicked on this to find out what the content of your HashMap is, the toString
method (docs) actually works with most objects. (note: a java array is not an object!)
So this woks perfectly fine for debugging purposes:
System.out.println(myMap.toString());
>>> {key1=value1, key2=value2}
Solution 15 - Java
Kotlin Answer
for ((key, value) in map.entries) {
// do something with `key`
// so something with `value`
}
You may find other solutions that include filterValues. Just keep in mind that retrieving a Key value using filterValues will include braces [].
val key = map.filterValues {it = position}.keys