How can I create array in Java?

Question

I need something that in PHP would look (2D array):

Array
(
[0] => Array
    (
        [name] => foo
        [desc] => some foo
    )

[1] => Array
    (
        [name] => bar
        [desc] => some bar
    )

)

All the java examples say that I should create "Integer [][] data;" or "String [][] data;" but here I have Int (index) and String... how to mix it? How to populate it ...datas[i]["name"] = "aa" ?? How to read it in another Loop like:

for(int i=start;i<start;i++)
{
   value = data[i]["name"]...???
}

Answer 1

As Pshemo say, java use only int as index for array.

You have plenty of solutions to achieve your objective. I will just present tree of them, both use an object container. Java is object programming, use them.

// Class declaration
public class SimpleContainer {

    private final String name;
    private final String description;

    public SimpleContainer(final String name, final String description) {
        this.name = name;
        this.description = description;
    }

    public String getName() {
        return name;
    }

    public String getDescription() {
        return description;
    }}

---

1, Use an array of object (not recommended):

 SimpleContainer[] simpleContainers = new SimpleContainer[3];
 simpleContainers[0] = new SimpleContainer("name 1", "description 1");
 simpleContainers[1] = new SimpleContainer("name 2", "description 2");
 simpleContainers[2] = new SimpleContainer("name 3", "description 3");

 for (int i = 0; i < simpleContainers.length; i++) {
        System.out.println(String.format("I am [%s] and my description is [%s]",
         simpleContainers[i].getName(),
         simpleContainers[i].getDescription()));
}

---

2. Use a list instead of your array

In Java a rule of thumb is to use array only for primitive type (like int, bytes, ...). And use list for others types. For more details, read:

1. When to use a List over an Array in Java?
2. more

Some simple example of list usage (same object) :

List<SimpleContainer> myList = new ArrayList<SimpleContainer>();
myList.add(new SimpleContainer("name 1", "description 1"));
myList.add(new SimpleContainer("name 2", "description 2"));
myList.add(new SimpleContainer("name 3", "description 3"));

// Use iterator (support remove object for most list implementations).
        Iterator<SimpleContainer> it = myList.iterator();

while(it.hasNext()) {
     SimpleContainer simpleContainer = it.next();
     System.out.println(String.format("I am [%s] and my description is [%s]",
     simpleContainer.getName(),
     simpleContainer.getDescription()));
}

// Or simple loop.
for (SimpleContainer simpleContainer : myList) {
     System.out.println(String.format("I am [%s] and my description is [%s]",
     simpleContainer.getName(),
     simpleContainer.getDescription()));
}

Understand the collections in Java is very important, just check a tutorial like : Simple tutorial about collections

---

3. Use a hashmap who represent an association between two objects. Hashmap is the preferred solution if the main action you want is to find any association.

    HashMap<String, String> myMap = new HashMap<>();
    myMap.put("name 1", "description 1");
    myMap.put("name 2", "description 2");
    myMap.put("name 3", "description 3");
   
    String description = myMap.get("name 1");
   
    Iterator<Map.Entry<String, String>> it =    myMap.entrySet().iterator();
   
     while (it.hasNext()) {
   
        Map.Entry pair = (Map.Entry)it.next();
       System.out.println(pair.getKey() + " = " + pair.getValue());
    }
   

---

4. Maybe you want to use a double index with int and string, in this case you can use one example of this page : Double key indexing

---

5. Finally you can use predicate (java 8 or guava librarie). There is an example of usage of guava predicate.

   public void ExamplePredicate() {
   List<SimpleContainer> myList = new ArrayList<SimpleContainer>();
   myList.add(new SimpleContainer("name 1", "description 1"));
   myList.add(new SimpleContainer("name 2", "description 2"));
   myList.add(new SimpleContainer("name 3", "description 3"));
   
   // Get one index :
   System.out.println(myList.get(1).getDescription());
   
   // Try to find an entry with name.
   Optional<SimpleContainer> optContainer = Iterables.tryFind(myList, new NameContainerPredicate("name 1"));
   if (optContainer.isPresent()) {
       System.out.println(optContainer.get().getDescription());
   }
   
   // Try to find an entry with name between two index.
   Optional<SimpleContainer> optContainer2 = Iterables.tryFind(myList.subList(1, 2), new NameContainerPredicate("name 1"));
   if (optContainer2.isPresent()) {
       System.out.println(optContainer2.get().getDescription());
   } else {
       System.out.println("No entry found");
   }
   
   // Get all entry with given name.
   List<SimpleContainer> containersList = Lists.newArrayList(Iterables.filter(myList.subList(1, 2), new NameContainerPredicate("name 1")));
   for (SimpleContainer simpleContainer : containersList) {
       System.out.println(String.format("Name [%s]  description [%s]", simpleContainer.getName(), simpleContainer.getDescription()));
   }
   }
   
   private static class NameContainerPredicate implements Predicate<SimpleContainer> {
   
   private final String name;
   
   public NameContainerPredicate(final String name) {
       this.name = name;
   }
   
   @Override
   public boolean apply(@Nullable final SimpleContainer input) {
       return input != null && equal(input.getName(), name);
   }
   }