In any computer program, control flow is the sequence of executing instructions. It is a vital aspect of control structures in Java that allows developers to create conditions or aspects of the program that can be repeated or alter how the program operates. Two major control flow categories are loops and conditionals. These structures are essential since they provide the ability to perform fundamental actions in almost all programs which include data processing, task repetition, and change of scenarios.
This article presents two concepts of the general control flow: loops and conditionals. Even though the concepts at first seem basic, once you learn to use these concepts to create more intricate and robust Java programs, you will understand that they are quite detailed.
The most common control structures of a program in Java are `if`, `else` and `else if`. These statements facilitate the selection by the program of different alternatives based on the evaluation of an expression or a condition that has been placed.
You can think of an `if` statement as a question that needs to be asked: If the answer to the condition is yes (i.e., the condition is satisfied) then execute the action(s) specified.
So, for instance, upon checking whether a number is positive and finding it is not, the `else` block can execute the code for the case when the negative or zero values are there.
In these cases, the first condition is satisfied in an if block which is followed by the else if statement. It has many simpler forms. It has a logic that uses various conditions to permit or block the specific block of code.
For instance, with the `else if`, you can try to check whether a given number is negative, positive or zero and do what is required.
An `else if` can be embedded within another `if`. Thus, the user can construct a more complicated control structure.
Yet, all these concepts should give the student as broad a picture as possible.
A `for` loop has three components: the initialization where the loop variable is initialized, the condition which enables the loop to be executed and the loop variable update after the loop has been run for one or more times.
The aforementioned loop construct utilizes an expression that is validated before the execution of every iteration. If the expression's value is true then the controlled code block of the loop is executed, and again the expression is verified. Contrarily, the controlled loop stops executing… if the expression inverts to be false.
This type of loop is useful if you want to make sure that the body of the loop runs at least once, even if it was not true to begin with.
These two statements certainly enable you to have better control over the execution of loops, especially over the combination of various conditions.
Nested loops are beneficial when performing multi-dimensional array processing or other repetitive tasks requiring multi-level iterations. In the same manner, nested conditionals are useful when you are trying to make 'within' decisions in a 'higher level' decision process.
This article presents two concepts of the general control flow: loops and conditionals. Even though the concepts at first seem basic, once you learn to use these concepts to create more intricate and robust Java programs, you will understand that they are quite detailed.
1. Java Conditional Statements (Switch Case)
In your program, Decision making is achieved through the use of conditionals. These statements allow for a case to be evaluated as true or false to determine what is to be run. In the event that the condition is true, one set of code is executed, and if the condition is false a different block runs instead.The most common control structures of a program in Java are `if`, `else` and `else if`. These statements facilitate the selection by the program of different alternatives based on the evaluation of an expression or a condition that has been placed.
1.1 The `if` Statement
The `if` statement is the most basic of all conditions. It is aimed at evaluating one proposition by either supporting its validity or invalidating it. In case the validated proposition is true, the program executes the code in the `if`, otherwise it does not.You can think of an `if` statement as a question that needs to be asked: If the answer to the condition is yes (i.e., the condition is satisfied) then execute the action(s) specified.
1.2 The `else` Statement
An else statement must be associated with an if statement so that a certain code will be executed if the condition in the if statement is false. It gives a different route to follow in case the if condition is false.So, for instance, upon checking whether a number is positive and finding it is not, the `else` block can execute the code for the case when the negative or zero values are there.
1.3 The `else if` Statement
You can also make use of the `else if` clause. if a second condition needs to be verified when the first one is not satisfied. The repetitive nature of problems is reflected in the first point. As a rule, it is possible to compute a number through a step by step process. Usually, you can write the logic in a tower of successive climbs.In these cases, the first condition is satisfied in an if block which is followed by the else if statement. It has many simpler forms. It has a logic that uses various conditions to permit or block the specific block of code.
For instance, with the `else if`, you can try to check whether a given number is negative, positive or zero and do what is required.
An `else if` can be embedded within another `if`. Thus, the user can construct a more complicated control structure.
Yet, all these concepts should give the student as broad a picture as possible.
2. Loops in Java
Loops are another fundamental control flow structure that allows you to repeat a block of code a number of times. This ease leads to several advantages throughout the life cycle of the application but in particular, while developing an application of the program. But this is a good way to avoid code writing multiple times in cases when the same operations have to be performed.2.1 The `for` Loop
In Java, probably one of the most common loops is the `for` loop. It enables you to perform a block of code a certain number of times. The `for` loop is useful when the exact number of iterations to be performed is known prior to the commencement of the loop. It is common practice when you want to cycle through an array of items or through the characters of a string.A `for` loop has three components: the initialization where the loop variable is initialized, the condition which enables the loop to be executed and the loop variable update after the loop has been run for one or more times.
2.2 The `while` Loop
The `while` loop is another genre of loops in Java programming language. In contrast with the `for` loop, the `while` loop remains in effect until implicitly or explicitly any of the conditions specified becomes false. It is almost always used when the number of iterations to be carried out is not predetermined but is conditional and must be satisfied at some point during the running of the program.The aforementioned loop construct utilizes an expression that is validated before the execution of every iteration. If the expression's value is true then the controlled code block of the loop is executed, and again the expression is verified. Contrarily, the controlled loop stops executing… if the expression inverts to be false.
2.3 The `do-while` Loop
The `do-while` loop and `while` loop perform the same functions however there is a controversy with the usage of the latter. `Do-while` loop ensures that the loop is executed at least once because the check for the condition occurs after the execution of code that is enclosed in the loop. As long as the condition is true after each execution of the loop, the loop will continue to execute regardless of how many iterations are completed.This type of loop is useful if you want to make sure that the body of the loop runs at least once, even if it was not true to begin with.
3. Breaking and Continuing Loops
Along with the regular loop constructs, Java offers two special commands `break` and `continue` which help in managing loops more efficiently.3.1 The `break` Statement
The `break` command is utilized for the early termination of a loop or breaks out from the loop. It does not matter if the condition is still satisfied, it simply cancels the entire loop. If you want to look for a result and there's no point of iterating, a `break` statement can be of use.3.2 The `continue` Statement
The `continue` is a statement that allows you to move on to the subsequent iteration of a loop while skipping the current one. Which means there exists a possibility of certain conditions where you don't want the whole loop to be removed but rather a specific iteration to be removed.These two statements certainly enable you to have better control over the execution of loops, especially over the combination of various conditions.
4. Nested Loops and Conditionals
There are also cases when it is necessary to meld loops with conditionals for more sophisticated cases. The term nested loop refers to the situation in which one loop is placed inside another loop, and nested conditional refers to when the second if statement is encompassed in the first if statement or loop.Nested loops are beneficial when performing multi-dimensional array processing or other repetitive tasks requiring multi-level iterations. In the same manner, nested conditionals are useful when you are trying to make 'within' decisions in a 'higher level' decision process.