Le Java si déclaration est utilisé pour tester la condition. Il vérifie booléen condition: vrai ou FAUX . Il existe différents types d'instructions if en Java.
pile en java
- si déclaration
- instruction if-else
- échelle si-sinon-si
- instruction if imbriquée
Java si instruction
L'instruction Java if teste la condition. Il exécute le si bloquer si la condition est vraie.
Syntaxe:
if(condition){ //code to be executed } 
Exemple:
//Java Program to demonstate the use of if statement. public class IfExample { public static void main(String[] args) { //defining an 'age' variable int age=20; //checking the age if(age>18){ System.out.print('Age is greater than 18'); } } } Testez-le maintenant Sortir:
Age is greater than 18
Déclaration Java if-else
L'instruction Java if-else teste également la condition. Il exécute le si bloquer si la condition est vraie sinon sinon bloquer est exécuté.
Syntaxe:
if(condition){ //code if condition is true }else{ //code if condition is false } 
Exemple:
//A Java Program to demonstrate the use of if-else statement. //It is a program of odd and even number. public class IfElseExample { public static void main(String[] args) { //defining a variable int number=13; //Check if the number is divisible by 2 or not if(number%2==0){ System.out.println('even number'); }else{ System.out.println('odd number'); } } } Testez-le maintenant Sortir:
inverser la chaîne en java
odd number
Exemple d'année bissextile :
Une année est bissextile si elle est divisible par 4 et 400. Mais pas par 100.
public class LeapYearExample { public static void main(String[] args) { int year=2020; if(((year % 4 ==0) && (year % 100 !=0)) || (year % 400==0)){ System.out.println('LEAP YEAR'); } else{ System.out.println('COMMON YEAR'); } } } Sortir:
LEAP YEAR
Utilisation de l'opérateur ternaire
Nous pouvons également utiliser l'opérateur ternaire (? :) pour effectuer la tâche de l'instruction if...else. C'est un moyen abrégé de vérifier l'état. Si la condition est vraie, le résultat de ? est retourné. Mais si la condition est fausse, le résultat de : est renvoyé.
Exemple:
public class IfElseTernaryExample { public static void main(String[] args) { int number=13; //Using ternary operator String output=(number%2==0)?'even number':'odd number'; System.out.println(output); } } Sortir:
odd number
Instruction d'échelle Java if-else-if
L'instruction à relais if-else-if exécute une condition parmi plusieurs instructions.
Syntaxe:
python convertit les octets en chaîne
if(condition1){ //code to be executed if condition1 is true }else if(condition2){ //code to be executed if condition2 is true } else if(condition3){ //code to be executed if condition3 is true } ... else{ //code to be executed if all the conditions are false } 
Exemple:
//Java Program to demonstrate the use of If else-if ladder. //It is a program of grading system for fail, D grade, C grade, B grade, A grade and A+. public class IfElseIfExample { public static void main(String[] args) { int marks=65; if(marks=50 && marks=60 && marks=70 && marks=80 && marks=90 && marks<100){ system.out.println('a+ grade'); }else{ system.out.println('invalid!'); } < pre> <p>Output:</p> <pre>C grade </pre> <p> <strong>Program to check POSITIVE, NEGATIVE or ZERO:</strong> </p> <pre> public class PositiveNegativeExample { public static void main(String[] args) { int number=-13; if(number>0){ System.out.println('POSITIVE'); }else if(number<0){ system.out.println('negative'); }else{ system.out.println('zero'); } < pre> <p>Output:</p> <pre>NEGATIVE </pre> <h2>Java Nested if statement</h2> <p>The nested if statement represents the <em>if block within another if block</em> . Here, the inner if block condition executes only when outer if block condition is true. </p> <p> <strong>Syntax:</strong> </p> <pre> if(condition){ //code to be executed if(condition){ //code to be executed } } </pre> <p> <strong>Example:</strong> </p> <pre> //Java Program to demonstrate the use of Nested If Statement. public class JavaNestedIfExample { public static void main(String[] args) { //Creating two variables for age and weight int age=20; int weight=80; //applying condition on age and weight if(age>=18){ if(weight>50){ System.out.println('You are eligible to donate blood'); } } }} </pre> <span> Test it Now </span> <p>Output:</p> <pre>You are eligible to donate blood </pre> <p> <strong>Example 2:</strong> </p> <pre> //Java Program to demonstrate the use of Nested If Statement. public class JavaNestedIfExample2 { public static void main(String[] args) { //Creating two variables for age and weight int age=25; int weight=48; //applying condition on age and weight if(age>=18){ if(weight>50){ System.out.println('You are eligible to donate blood'); } else{ System.out.println('You are not eligible to donate blood'); } } else{ System.out.println('Age must be greater than 18'); } } } </pre> <span> Test it Now </span> <p>Output:</p> <pre> You are not eligible to donate blood </pre> <hr></0){></pre></100){> Programme pour vérifier POSITIF, NÉGATIF ou ZÉRO :
public class PositiveNegativeExample { public static void main(String[] args) { int number=-13; if(number>0){ System.out.println('POSITIVE'); }else if(number<0){ system.out.println(\'negative\'); }else{ system.out.println(\'zero\'); } < pre> <p>Output:</p> <pre>NEGATIVE </pre> <h2>Java Nested if statement</h2> <p>The nested if statement represents the <em>if block within another if block</em> . Here, the inner if block condition executes only when outer if block condition is true. </p> <p> <strong>Syntax:</strong> </p> <pre> if(condition){ //code to be executed if(condition){ //code to be executed } } </pre> <p> <strong>Example:</strong> </p> <pre> //Java Program to demonstrate the use of Nested If Statement. public class JavaNestedIfExample { public static void main(String[] args) { //Creating two variables for age and weight int age=20; int weight=80; //applying condition on age and weight if(age>=18){ if(weight>50){ System.out.println('You are eligible to donate blood'); } } }} </pre> <span> Test it Now </span> <p>Output:</p> <pre>You are eligible to donate blood </pre> <p> <strong>Example 2:</strong> </p> <pre> //Java Program to demonstrate the use of Nested If Statement. public class JavaNestedIfExample2 { public static void main(String[] args) { //Creating two variables for age and weight int age=25; int weight=48; //applying condition on age and weight if(age>=18){ if(weight>50){ System.out.println('You are eligible to donate blood'); } else{ System.out.println('You are not eligible to donate blood'); } } else{ System.out.println('Age must be greater than 18'); } } } </pre> <span> Test it Now </span> <p>Output:</p> <pre> You are not eligible to donate blood </pre> <hr></0){> Instruction if imbriquée Java
L'instruction if imbriquée représente le si bloc dans un autre si bloc . Ici, la condition de bloc if interne s'exécute uniquement lorsque la condition de bloc if externe est vraie.
Syntaxe:
tri par insertion en Java
if(condition){ //code to be executed if(condition){ //code to be executed } } Exemple:
//Java Program to demonstrate the use of Nested If Statement. public class JavaNestedIfExample { public static void main(String[] args) { //Creating two variables for age and weight int age=20; int weight=80; //applying condition on age and weight if(age>=18){ if(weight>50){ System.out.println('You are eligible to donate blood'); } } }} Testez-le maintenant Sortir:
You are eligible to donate blood
Exemple 2 :
//Java Program to demonstrate the use of Nested If Statement. public class JavaNestedIfExample2 { public static void main(String[] args) { //Creating two variables for age and weight int age=25; int weight=48; //applying condition on age and weight if(age>=18){ if(weight>50){ System.out.println('You are eligible to donate blood'); } else{ System.out.println('You are not eligible to donate blood'); } } else{ System.out.println('Age must be greater than 18'); } } } Testez-le maintenant Sortir:
You are not eligible to donate blood