I have a list of object :
List<Object[]> list = new ArrayList<>();
Object[] object = {"test", "test1", "test2"};
list.add(object);
List contains some data.
I have another string String str = "test";
I am using below code. What are best other ways:
for (Object []object1 : list) {
for (Object obj : object1) {
if (obj.equals("test")) {
System.out.println("true");
}
}
}
How to check this string present in above list with minimum of code.
Java 8 introduced Streams which are powerful, yet code-compact as you demanded. This answer uses more features of Java 8 sucha as Lambdas and Method References.
Here is a one-liner instruction:
boolean containsObject = list.stream().flatMap(Arrays::stream).filter(s->str.equals(s) ).findFirst().isPresent();
Here how it works:
boolean containsObject = list.stream() // Turning the List into a Stream of Arrays
.flatMap(Arrays::stream) // flattening the 2D structure into a single-dimensional stream of Objects (Note: using a Method reference)
.filter(s->str.equals(s)) // Filtering the flat stream to check for equality (Note: using a Lambda expression)
.findFirst() // Demands to find the first Occurence that passed the Filter test
.isPresent(); // Collapse the stream and returns the result of the above demand (Note: the Stream makes no computation until this instruction)
This solution is code-compact, and brings the nice features of Streams such as parallelization and laziness.
If you convert the Object[]s to lists, then you can call their contains(Object). You could either have list be a List<List<Object>>, or you could leave it with Object[] and wrap the Object[]s in a List as-needed.
Example of the "convert as needed":
for(Object[] object1 : list)
if(Arrays.asList(object1).contains("test"))
System.out.println("true");
Personally, I would have list be a List<List>. Whenever you add to it, just wrap your arrays in a list. Assuming arr is an Object[], that means list.add(Arrays.asList(arr));.
Alexander's answer is also correct (I think; I didn't examine it too closely), but I find long strings of stream operators to be less readable. If you disagree with my opinion on that, then use the stream operators.
