Array in method - JAVA

Question

I saw this code in one of the tutorials. There isn't any error with it, but I just don't understand the code. Could someone guide me?

int trying[] = {3,4,5,6,7};
change (trying);

for(int y: trying) {
    System.out.println(y);
    }
}
public static void change (int x[]) {
    for ( int counter = 0; counter < x.length ; counter++){
        x[counter] += 5;
     }
}

Able to explain this part for me?

for(int y: trying) {
    System.out.println(y);
 }

I don't understand especially this line of code:

for (int y : trying)

Answer 1

Java for-Each loop Syntax:

for(data_type variable : array | collection){} 

Advantage:

• It makes the code more readable.

in your example

 for(int y: trying){
     System.out.println(y);
 }

simply means like int y will iterate over all the values in trying. Like,

for(int i=0;i < trying.length;i++){
      int y = trying[i]; 
      System.out.println(y);
}

Collection:

 List<String> someList = new ArrayList<String>();
    // add "monkey", "donkey", "skeleton key" to someList

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

same as:

 for (Iterator<String> itr = someList.iterator(); itr.hasNext(); ) {
       String item = itr.next();
       System.out.println(item);
    } 

as it discussed earlier in this post

Answer 2

It's a for-each loop, a convenient way to loop over an array, a Collection, or more generally any Iterable.

For example, looping over an array of integers int[] trying, you can do:

for(int i=0; i<trying.length; i++) {
  int y = trying[i];
  // stuff with y
}

or using a while, an iterator... But this is a bunch of character, we are lazy and our fingers are tired. So here is shorter way to do such frequent operation:

for( int y : trying ) {
  // stuff with y
}

Behind the hood, the extended for cache an Iterator for any Iterable, or the index for an array, here is the JLS specification.

Answer 3

for(int y: trying) is an implementation of foreach loop in java. This can be understood as:

for(int i = 0; i< trying.length; i ++){
    int y = trying[i];
    System.out.println(y);
}

the Java documentation states

The for-each construct is also applicable to arrays, where it hides the index variable rather than the iterator.

Answer 4

Okay, so trying[] is an array of integers. The function change() takes trying[] as input and +5 to every integer in trying[]. And the for loop that you are asking about is just syntactic sugar that can shorten code.

Look at the doc links and try running it in eclipse or some IDE.

Answer 5

I hope i can give you the information want or need.

Int trying[] is an array of integer.

with the for loop you loop trough the trying[] array, and everytime you circle trough you send a message to the console.

Then you have your second loop

so if you int counter is smaller then the length of the array x[] then you keep circling trough the loop. as soon as the counter reaches the same length or value as the x[] then the loop stops.

for(int y: trying) {
    System.out.println(y);
    }
}

So the example above isnt really that hard, the loop will continue to the point where i is greater or the same as trying.

with this information you can figure out the last for loop by yourself:

https://docs.oracle.com/javase/tutorial/java/nutsandbolts/operators.html

Answer 6

This is called a foreach loop. So in words it says:

For each item "y" in the array "trying" - do something (here: print it).

It is very convenient in the case you don't care how often you loop but just want to address every item in the array/collection.

Alternatively you could just use the "normal" for loop as you used it in the change method.

Answer 7

It says, run the code in { ... } for each object in trying.

Datatype is int, because trying is an array of int.

"y" is a variable that holds an object from trying (one at a time).

For example, when looping first time, y gets first value (3) from the array and runs the code between { and }. Then, y gets second value (4) from the array and run the same code again....and so on.

In this case, it will print a value of y for each object in trying.

for(int y: trying)
{
    System.out.println(y);
}

Datatype mentioned in for loop must be the same as the type of array. for Example,

for (String s : allLines) { ... }
for (Member m : allMembers) { ... }