Map.Entry class
In this chapter you will learn:
Map.Entry in a Map
Map is a structure to store key and value pair.
Sometime we would like to access a map pair by pair.
One way to access all pairs in a map is to use the Map.Entry class.
The entrySet() method returns a Set of Map.Entry objects.
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
//from j a v a 2s.com
public class Main {
public static void main(String[] a) {
Map<String,String> map = new HashMap<String,String>();
map.put("key1", "value1");
map.put("key2", "value2");
map.put("key3", "value3");
Set set = map.entrySet();
Iterator iter = set.iterator();
while (iter.hasNext()) {
Map.Entry entry = (Map.Entry) iter.next();
}
}
}
Get key and value from the Map.Entry
Once we have the Map.Entry we can access the key and value fairly easy.
import java.util.Iterator;
import java.util.Map;
import java.util.Properties;
//from j av a2 s .com
public class Main {
public static void main(String[] a) {
Properties props = System.getProperties();
Iterator iter = props.entrySet().iterator();
while (iter.hasNext()) {
Map.Entry entry = (Map.Entry) iter.next();
System.out.println(entry.getKey() + " -- " + entry.getValue());
}
}
}
The code above generates the following result.
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What you will learn in the next chapter:
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