Control Flow Statements in Java
Control flow statements in Java govern the sequence and execution of code, directing the program’s flow based on conditions and loops. Do read our blog on Learn Java Programming
Try that all code will not every time means when we login at the time login code will run and when we log out at that time logout code will run
if(){
}
if(true){
}
//here is the condition should be true then only the code which is written in curly braces will execute and vice versa
const isUserloggedIn = true
if (isUserloggedIn){
}
//here if the condition will run
For checking the condition we have condition operators like less than <, greater than < , less than equal to <=, greater than equal to >=, equality operator = =, not equal !=, strict equality operator = = = it is use for type checking.
= Single equal is for assignment operator
if (2 == ‘2’){
console.log(“execute”);
}
//here if condition will run
if (2 == ‘2’){
console.log(“execute”);
}
console.log(“Nor execute”);
//here both will print
if (2 != 3){
console.log(“execute”);
}
console.log(“Nor execute”);
//here both will print
if (2 !== 3){
console.log(“execute”);
}
console.log(“Nor execute”);
//here both will print
const isUserloggedIn = true
const temperature = 41
if ( temperature < 50 ){
console.log(“less than 50”);
}
console.log(“temperature is greater than 50”);
//here both will print
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const isUserloggedIn = true
const temperature = 41
if ( temperature < 50 ){
console.log(“less than 50”);
} else {
console.log(“temperature is greater than 50”);
}
//here true part will only execute
const isUserloggedIn = true
const temperature = 41
if ( temperature < 50 ){
console.log(“less than 50”);
} else {
console.log(“temperature is greater than 50”);
}
const score = 200
if (score > 100) {
let power = “fly”
console.log(`User power: ${power}`);
}
//output is User power: fly
const score = 200
if (score > 100) {
let power = “fly”
console.log(`User power: ${power}`);
}
console.log(`User power: ${power}`);
console.log(“Run”);
//here we will get error that power is not defined becz we are calling the power variable outside the scope.
//Short hand property
const balance = 1000
if (balance > 500) console.log(“test”),console.log(“test2”);
//output test test2
//nested if else
if (balance < 500) {
console.log(“less than 500”);
} else if (balance < 750) {
console.log(“less than 750”);
} else if (balance < 900) {
console.log(“less than 750”);
} else {
console.log(“less than 1200”);
}
//&& operator
const userLoggedIn = true
const debitCard = true
if (userLoggedIn && debitCard && 2==2) {
console.log(“Allow to buy course”);
}
const userLoggedIn = true
const debitCard = true
const loggedInFromGoogle = false
const loggedInFromEmail = true
if (userLoggedIn && debitCard && 2==3) {
console.log(“Allow to buy course”);
}
if (loggedInFromGoogle || loggedInFromEmail) {
console.log(“User logged in”); } //User logged in
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When we check a value with multiple conditions at that time we use switch case=>
switch case is like we are having so many looks and a single key and the key matches with the particular look we will open that lock
const month = “march”
switch (month) {
case 1:
console.log(“January”);
break;
case 2:
console.log(“feb”);
break;
case 3:
console.log(“march”);
break;
case 4:
console.log(“april”);
break;
default:
console.log(“default case match”);
break;
}
Output is=> march
The importance of break is that if we remove break from the end of every line and suppose any one condition matches the particular case then the case will print as an output and the cases that are present after that match condition rest of the cases will print except default case means default case will not print, it will only print when no cases will match. So to resolve this problem we use a break statement. So we can say that break will break the control flow.
Suppose we have string value that =>
//switch case with string value
const month = “march”
switch (month) {
case “jan”:
console.log(“January”);
break;
case “feb”:
console.log(“feb”);
break;
case “march”:
console.log(“march”);
break;
case “april”:
console.log(“april”);
break;
default:
console.log(“default case match”);
break;
}
Nullish Coalescing Operator (??) =>
In this mostly we talk about null and undefined
let val1;
val1 = 5 ?? 10
console.log(val1); //5
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As we can see we are getting the first value as and output so the use of => ?? => is when we are calling data from a database or using Firebase at that time we are not getting a response directly we are getting two values so becz of this there are changes that we will get a null response or there is chances that we will not get any response means we will get undefine by these types of issues our whole code structure will effect. So to handle such a case =>Nullish Coalescing Operator (??). We can also say that this operator is a safety check of null value
let val1;
val1 = null ?? 10
console.log(val1); //10
let val1;
val1 = undefined ?? 20
console.log(val1); //20
let val1;
val1 = null ?? 10 ?? 20
console.log(val1); //10
Terniary Operator=>
condition ? true : false
const iceTeaPrice = 100
iceTeaPrice <= 80 ? console.log(“less than 80”) : console.log(“more than 80”) //more than 80
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