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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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What is fail-fast in java?
A fail-fast system is nothing but immediately report any failure that
is likely to lead to failure. When a problem occurs, a fail-fast system
fails immediately. In Java, we can find this behavior with iterators.
Incase, you have called iterator on a collection object, and another
thread tries to modify the collection object, then concurrent modification
exception will be thrown. This is called fail-fast.
The greatest obstacle to discovery is not ignorance; it is the illusion of knowledge.
-- Daniel J. Boorstin
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