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Java 8 - forEach method example with Map
forEach is a new method introduced in Java 8 to iterate over collections. Here is an example on forEach method
to iterate over Map.
package com.java2novice.java8;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
public class ForEachMapEx {
public static void main(String a[]) {
Map<String, String> countryMap = new HashMap<>();
countryMap.put("India", "Delhi");
countryMap.put("USA", "Washington, D.C.");
countryMap.put("Japan", "Tokyo");
countryMap.put("Canada", "Ottawa");
// iterate through Map normal way
ForEachMapEx.iterateMap(countryMap);
// iterate through Map using forEach method
ForEachMapEx.iterateMapUsingForEach(countryMap);
}
public static void iterateMap(Map<String, String> countryMap) {
System.out.println("<----------Iterating in normal way------------->");
for(Entry<String, String> entry:countryMap.entrySet()) {
System.out.println("Country: "+entry.getKey()+" : Capital: "+entry.getValue());
}
}
public static void iterateMapUsingForEach(Map<String, String> countryMap) {
System.out.println("\n<----------Iterating using forEach method------------>");
countryMap.forEach((k,v)->System.out.println("Country: "+k+" : Capital: "+v));
countryMap.forEach((k,v)->{
// you can implement some business logic here..
});
}
}
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| Output: |
<----------Iterating in normal way------------->
Country: Canada : Capital: Ottawa
Country: USA : Capital: Washington, D.C.
Country: Japan : Capital: Tokyo
Country: India : Capital: Delhi
<----------Iterating using forEach method------------>
Country: Canada : Capital: Ottawa
Country: USA : Capital: Washington, D.C.
Country: Japan : Capital: Tokyo
Country: India : Capital: Delhi
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Java 8 forEach method examples
- Java 8 forEach example with Map
- Java 8 forEach example with List
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When to use LinkedList or ArrayList?
Accessing elements are faster with ArrayList, because it is index based.
But accessing is difficult with LinkedList. It is slow access. This is
to access any element, you need to navigate through the elements one by
one. But insertion and deletion is much faster with LinkedList, because
if you know the node, just change the pointers before or after nodes.
Insertion and deletion is slow with ArrayList, this is because, during
these operations ArrayList need to adjust the indexes according to
deletion or insetion if you are performing on middle indexes. Means,
an ArrayList having 10 elements, if you are inserting at index 5, then
you need to shift the indexes above 5 to one more.
It’s not that I’m so smart, it’s just that I stay with problems longer.
-- Albert Einstein
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