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There are multiple ways to iterate or loop a Map in Java.
Using foreach in Java 8
If you using Java 8 this is the easiest way to loop the Map.
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// {
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
public class Main {
public static void main(String[] args) {
// }
Map<Integer, String> customers = new HashMap<>();
customers.put(1, "Jhon");
customers.put(2, "Smith");
customers.put(3, "Sally");
System.out.println("Using foreach in Java 8");
customers.forEach((id, name) -> {
System.out.println("Key : " + id + " value : " + name);
});
//{
}
}
//}
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Using stream() in Java 8
This is also using in Java 8. If you want to filter some data while looping this is one of best way to do that.
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// {
Map<Integer, String> customers = new HashMap<>();
customers.put(1, "Jhon");
customers.put(2, "Smith");
customers.put(3, "Sally");
System.out.println("");
customers.entrySet().stream().forEach(e ->
System.out.println("Key : " + e.getKey() + " value : " + e.getValue())
);
//{
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Using entrySet()
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// {
Map<Integer, String> customers = new HashMap<>();
customers.put(1, "Jhon");
customers.put(2, "Smith");
customers.put(3, "Sally");
for (Map.Entry<Integer, String> entry : customers.entrySet()) {
System.out.println("Key : " + entry.getKey() + " value : " + entry.getValue());
}
//{
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Using keySet()
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// {
Map<Integer, String> customers = new HashMap<>();
customers.put(1, "Jhon");
customers.put(2, "Smith");
customers.put(3, "Sally");
for (Integer key : customers.keySet()) {
System.out.println("Key : " + key + " value : " + customers.get(key));
}
//{
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Using iterator through map
This way is more suitable for when you need to remove some data while iterating.
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// {
Map<Integer, String> customers = new HashMap<>();
customers.put(1, "Jhon");
customers.put(2, "Smith");
customers.put(3, "Sally");
Iterator<Map.Entry<Integer, String>> iterator = customers.entrySet().iterator();
while (iterator.hasNext()) {
Map.Entry entry = iterator.next();
System.out.println("Key : " + entry.getKey() + " value : " + entry.getValue());
}
//{
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Using iterator through the KeySet
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// {
Map<Integer, String> customers = new HashMap<>();
customers.put(1, "Jhon");
customers.put(2, "Smith");
customers.put(3, "Sally");
Iterator<Integer> iterator = customers.keySet().iterator();
while (iterator.hasNext()) {
Integer key = iterator.next();
System.out.println("Key : " + key + " value : " + customers.get(key));
}
//{
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Original post :- http://mydevgeek.com/6-ways-iterate-loop-map-java/
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