Map element adding
In this chapter you will learn:
Add key value pair to a map
When adding entries to a Map we have to provide both key and value.
In other words, we have to put value into a Map pair by pair.
import java.util.HashMap;
import java.util.Map;
//from j a va2s.c o m
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");
System.out.println(map);
}
}
Create map from another map
We can choose to add all key and value pairs from another map
in one method call with putAll.
import java.util.HashMap;
import java.util.Map;
//from j av a 2 s . co m
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");
map.put(null, null);
Map<String,String> map2 = new HashMap<String,String>();
map2.put("key4", "value4");
map2.put("key5", "value5");
map2.put("key6", "value6");
map.putAll(map2);
System.out.println(map);
}
}
The code above generates the following result.
Next chapter...
What you will learn in the next chapter:
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