Modify property value of the objects in list using Java 8 streams
Java 8Java StreamJava 8 Problem Overview
I have a list of Fruit
objects in ArrayList and I want to modify fruitName
to its plural name.
Refer the example:
@Data
@AllArgsConstructor
@ToString
class Fruit {
long id;
String name;
String country;
}
List<Fruit> fruits = Lists.newArrayList();
fruits.add(new Fruit(1L, "Apple", "India"));
fruits.add(new Fruit(2L, "Pineapple", "India"));
fruits.add(new Fruit(3L, "Kiwi", "New Zealand"));
Comparator<Option> byNameComparator = (e1, e2) -> e1.getName().compareToIgnoreCase(e2.getName());
fruits = fruits.stream().filter(fruit -> "India".equals(fruit.getCountry()))
.sorted(byNameComparator).collect(Collectors.toList());
List<Fruit> fruitsWithPluralNames = Lists.newArrayList();
for (Fruit fruit : fruits) {
fruit.setName(fruit.getName() + "s");
fruitsWithPluralNames.add(fruit);
}
System.out.println(fruitsWithPluralNames);
// which prints [Fruit(id=1, name=Apples, country=India), Fruit(id=2, name=Pineapples, country=India), Fruit(id=3, name=Kiwis, country=New Zealand)]
Do we have any way to achieve same behavior using Java 8 streams ?
Java 8 Solutions
Solution 1 - Java 8
If you wanna create new list, use Stream.map
method:
List<Fruit> newList = fruits.stream()
.map(f -> new Fruit(f.getId(), f.getName() + "s", f.getCountry()))
.collect(Collectors.toList())
If you wanna modify current list, use Collection.forEach
:
fruits.forEach(f -> f.setName(f.getName() + "s"))
Solution 2 - Java 8
You can use just forEach
. No stream at all:
fruits.forEach(fruit -> fruit.setName(fruit.getName() + "s"));
Solution 3 - Java 8
You can use peek
to do that.
List<Fruit> newList = fruits.stream()
.peek(f -> f.setName(f.getName() + "s"))
.collect(Collectors.toList());
Solution 4 - Java 8
just for modifying certain property from object collection you could directly use forEach with a collection as follows
collection.forEach(c -> c.setXyz(c.getXyz + "a"))
Solution 5 - Java 8
We can change the property via map without creating new objects. Below method increase the age by 2. It will modify your original list
List<Employee> l2=list.stream().map(t->{
t.setAge(t.getAge()*2);
return t;
}
).collect(Collectors.toList());
Solution 6 - Java 8
You can do it using streams map function like below, get result in new stream for further processing.
Stream<Fruit> newFruits = fruits.stream().map(fruit -> {fruit.name+="s"; return fruit;});
newFruits.forEach(fruit->{
System.out.println(fruit.name);
});
Solution 7 - Java 8
You can use map from streams.
fruits.map(i-> {
i.setFruit();
return i;
}).collect(Collectors.toList();