El Java declaració si s'utilitza per comprovar la condició. Es comprova booleà condició: veritat o fals . Hi ha diversos tipus de declaracions if a Java.
qui es urfi javed
- declaració si
- declaració if-else
- si-més-si escala
- declaració if imbricada
Java if Statement
La sentència if de Java prova la condició. Executa el si es bloqueja si la condició és certa.
Sintaxi:
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'); } } } Prova-ho ara Sortida:
Age is greater than 18
Declaració Java if-else
La sentència if-else de Java també prova la condició. Executa el si es bloqueja si la condició és certa en cas contrari altre bloc s'executa.
Sintaxi:
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'); } } } Prova-ho ara Sortida:
odd number
Exemple d'any de traspàs:
Un any és salt, si és divisible per 4 i 400. Però no per 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'); } } } Sortida:
LEAP YEAR
Utilitzant l'operador ternari
També podem utilitzar l'operador ternari (? :) per dur a terme la tasca de la instrucció if...else. És una manera taquigràfica de comprovar l'estat. Si la condició és certa, el resultat de ? es retorna. Però, si la condició és falsa, es retorna el resultat de :.
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); } } Sortida:
significat xdxd
odd number
Declaració Java if-else-if ladder
La instrucció d'escala if-else-if executa una condició a partir de diverses sentències.
Sintaxi:
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){> Programa per comprovar POSITIU, NEGATIU o ZERO:
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){> Declaració if niada de Java
La sentència if imbricada representa el bloc si dins d'un altre bloc si . Aquí, la condició de bloc si interna s'executa només quan la condició de bloc si externa és certa.
Sintaxi:
miniaplicació d'applet
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'); } } }} Prova-ho ara Sortida:
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'); } } } Prova-ho ara Sortida:
You are not eligible to donate blood