![]() ![]() loop exits when i gets to 100 and the boolean condition evaluates to false.step value increments the loop index by 1 after every loop.boolean condition tests that the loop index is less than 100.Here is a simple for loop incrementing values from 0 to 99. Java for loops are structured to follow this order of execution:Ģ) boolean condition – if true, continue to next step if false, exit loopĥ) repeat from step 2 (boolean condition) For example, when looping over an array of numbers you will need to loop over as many times as there are elements in the array. For Loopįor loops are best used when you know how many times you have to loop over something. Throughout this tutorial, we’ll be referring to these concepts as we introduce each loop. loop body – execute the main part of the loop that does the processing.step value (update value) – an update to the loop variable(s).boolean condition – this is a boolean expression that determines whether to continue looping for one more iteration.loop initialization – setting the initial value of variable(s) to be used in the loop.Loops ConceptsĪll loops in Java use the same building blocks that we’re going to define here. And sometimes the programmer won’t know in advance how many pieces of data the program will encounter so looping will be necessary.įor example, loops can be used to iterate over a list of returned database records, to sort a list of numbers, or to read a file line by line. It’s better and more efficient to use loops than having to explicitly write the code to process each action. The basic reason for using loops is when a repetitive action needs to be taken over and over. Each thread has its own obj variable, but those are all initialized to point to the same instance, and the threads never assign their obj variables: The threads mutate the one shared instance instead.Loops are used in most programs for a variety of reasons. ![]() In your second example, there is only ever one MyObj instance. Since each of your threads has its own counter, and each one constructs its own new sequence of Integer objects to assign to counter, the threads run entirely independent of each other. Store a reference to the new object into the counter variable.Construct a new Integer object with the new value, and finally.Compute a new int value, equal to 1+ the previous value,.Get the int value of the Integer object,.fetch the value of the counter variable, which is a reference to an immutable Integer object.In particular, this statement does not do what you seem to think it does: counter++ In a nutshell: The difference between your two implementations is that your MyObj class is mutable, but Integer is immutable. Again, beware of the console printing lines out of chronological order. Public Threaded(String name, Integer counter) Įxample run. Threaded t = new Threaded("Thread " + i, counter) Can someone give an explanation of what's going and how I'd make the first behave in a similar manner to the second. When I run these the output is different and not what I expected. One passes an Integer to the thread and the thread increments it and the other passes an object that has an inner Integer which is incremented.
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