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How to use forEach() method as loop in Java 8?

+2 votes
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How to use forEach() method as loop in Java 8, please explain with example?

posted Jan 12, 2016 by anonymous

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1 Answer

+1 vote

forEach and Map

1.1 Normal way to loop a Map.

Map<String, Integer> items = new HashMap<>();
    items.put("A", 10);
    items.put("B", 20);
    items.put("C", 30);
    items.put("D", 40);
    items.put("E", 50);
    items.put("F", 60);

    for (Map.Entry<String, Integer> entry : items.entrySet()) {
        System.out.println("Item : " + entry.getKey() + " Count : " + entry.getValue());
    }

1.2 In Java 8, you can loop a Map with forEach + lambda expression.

Map<String, Integer> items = new HashMap<>();
items.put("A", 10);
items.put("B", 20);
items.put("C", 30);
items.put("D", 40);
items.put("E", 50);
items.put("F", 60);

items.forEach((k,v)->System.out.println("Item : " + k + " Count : " + v));

items.forEach((k,v)->{
    System.out.println("Item : " + k + " Count : " + v);
    if("E".equals(k)){
        System.out.println("Hello E");
    }
});

2. forEach and List

2.1 Normal for-loop to loop a List.

List<String> items = new ArrayList<>();
    items.add("A");
    items.add("B");
    items.add("C");
    items.add("D");
    items.add("E");

    for(String item : items){
        System.out.println(item);
    }

2.2 In Java 8, you can loop a List with forEach + lambda expression or method reference.

List<String> items = new ArrayList<>();
    items.add("A");
    items.add("B");
    items.add("C");
    items.add("D");
    items.add("E");

    //lambda
    //Output : A,B,C,D,E
    items.forEach(item->System.out.println(item));

    //Output : C
    items.forEach(item->{
        if("C".equals(item)){
            System.out.println(item);
        }
    });

    //method reference
    //Output : A,B,C,D,E
    items.forEach(System.out::println);

    //Steam and filter
    //Output : B
    items.stream()
        .filter(s->s.contains("B"))
        .forEach(System.out::println);
answer Jan 19, 2016 by Karthick.c
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0 votes
How to use foreach loop for filtering on the API to show the match value from database?

I am working on an API integration. Now I have a problem. First I am trying to show all specific city hotels, which city is having in my database. First FOREACH worked as well its search hotel by my database city, but on Second FOREACH I am trying to show First FOREACH city hotels show only match hotel which hotels matches from database and its not worked.

My Task is: 1st search by city which city have on my database and 2nd time search in 1st time hotel and showed hotel only match my database hotel.

1st foreach:

if($RowCount>0){
            foreach($Results as $Result){
                foreach($api_array as &$value){
                    if($Result['county'] == $value['address']['city']){ 
                        $final_array[] = $value; 
                    } 
                } 
            }
        }

2nd foreach:

foreach($final_array as &$display){
            var_dump($display);
            if($Result['hotel'] == $display['property_name']){ 
                $final_array2[] = $display; 
            }  
        }

full code:

foreach($array as $api_array){
        $final_array = array(); 
        $Results = $wpdb->get_results( "select * FROM hotels where county = '$countyname'",ARRAY_A );
        $RowCount  =  $wpdb->num_rows;

        if($RowCount>0){
            foreach($Results as $Result){
                foreach($api_array as &$value){
                    if($Result['county'] == $value['address']['city']){ 
                        $final_array[] = $value; 
                    } 
                } 
            }
        }
        foreach($final_array as &$display){
            if($Result['hotel'] == $display['property_name']){ 
                $final_array2[] = $display; 
            }  
        }
    }
...