How to make class executable in forEach loop?

Question

If I have a class

public class Op {
    public Map<String, String> ops;
}

How can I make it executable in forEach loop?

for (String key : op) {
    System.out.println(op.ops.get(key))
}

UPD

Here is my solution

Op op = new Op(new HashMap<String, String>() {{
    put("a", "1");
    put("b", "2");
    put("c", "3");
}});

for (String key : op) System.out.println(op.map.get(key));

class Op implements Iterable<String> {    
    Map<String, String> map;
    public Op(Map<String, String> map) {
        this.map = map;
    }   
    public Iterator<String> iterator() {
        return map.keySet().iterator();
    }
}

But I'm not sure about verbosity. Is it too verbose? Maybe there is a much concise way to implement it?

http://tutorials.jenkov.com/java-generics/implementing-iterable.html — buxter, Jan 08 '15 at 13:24
Yes. It's good example. But I don't need to write a separate Iterator class. I need a code as concise as possible, with minimal amount of lines of code. — barbara, Jan 08 '15 at 13:35

score 2 · Accepted Answer · edited May 23 '17 at 12:28

2

You are interested in looping over a SetEntry list.

for (Map.Entry<String, String > entry : ops.entrySet()) {
    String key = entry.getKey();
    String value = entry.getValue();
    // ...
}

Propable duplicate of: Iterate through a HashMap

edited May 23 '17 at 12:28

Community

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1

answered Jan 08 '15 at 13:24

Beri

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score 0 · Answer 2 · answered Jan 08 '15 at 13:24

In this exact case, use #entrySet, #keySet or #values as specified in the API docs.

In a general case, an object is iterable using the enhanced for loop, if it is implementing the interface Iterable. The most of the standard java collections are implementing this interface.

score 0 · Answer 3 · answered Jan 08 '15 at 17:58

public class Op implements Iterable<Map.Entry<String,String>> {
public Map<String, String> ops;

@Override
public Iterator<Map.Entry<String,String>> iterator() {
    return ops.entrySet().iterator();
}

}

Example:

for (Map.Entry<String, String> n : testOp){
        System.out.println("Key: " + n.getKey() + " Value: " + n.getValue());
    }

How to make class executable in forEach loop?

3 Answers3