Branch Statements or Conditional Statements

These Statements allow you to create programs where decisions are taken based on the expression specified in the statements

1. if statement
2. if else statement
3. switch statement

If statement

if block is executed only when the if expression is true otherwise, the if block is skipped

Flow chart

flowchart TD A[START] --> B{Condition} B --> |True| C[Execute if block] C --> D B --> |False| D(Continue execution of other statements)

Examples

Ex1:

class Demo22{
    public static void main(String[] args) {
        int age = 16;
        if(age < 18){
            System.out.println("not eligible to vote");
        }
    }
}

Ex2:

class Demo23{
    public static void main(String[] args) {
        int age =16;
        if(age < 18){
            System.out.println("not eligible to vote");
        }
        age = age + 2;
        System.out.println("Age of the persion is " + age);
    }
}

Note: In the above case only the block code of if statement
is executed if the experession is true and the other 
statements get executed as usual

if else statement

Flow chart

flowchart TD A[START] --> B{if expression} B --> |True| C[Execute if block] B --> |False| D[Execute else block] C --> E D --> E(Continue execution of other statements)

Examples

class Demo24{
    public static void main(String[] args) {
        int a =10, b =20;
        if(a > b){
            System.out.println("a is greater than b");
        }else {
            System.out.println("b is greater than a");
        }
    }
}

class Demo27{
    public static void main(String[] args) {
        int a = 10, b=20, c=30;
        if(a > b && a > c){
            System.out.println("a is greater than b and c");
        }else if(b > a && b > c){
            System.out.println("b is greater than a and c");
        } else{
            System.out.println("c is greater than a and b");
        }
    }
}

Notes

1. An if statement can be used without an else statement
2. Multiple if else statements can be used in a program
3. Once an if else statement causes an action in a program, then the remaining if else statements will be ignored

switch case statement

The switch case statement is used to select an action from a given set of actions, based on a specified expression

Syntax

    switch(expression/variables){
        case value1 : statement1;
        case value2 : statement2;
        case value3 : statement3;
        default : default_statement;
    }   

the expression/variable in the above syntax can be any expression depicting a char, byte, int or enum variable. the switch case also support some wrapper class like integer, byte and short

Example

class Demo28{
    public static void main(String[] args) {
        char country='i';
        switch(country){
            case 'b' :
                System.out.println("Brasil");
                break;
            case 'n' :
                System.out.println("New Zealand");
                break;
            case 'i';
                System.out.println("India");
                break;
            default:
                System.out.println("Invalid");
        }
    }
}

Usages of conditional statements

When can we use if else and switch case? if Statements are used to evaluate boolean expression. A switch statement allows a variable to be tested for equality against a list of values. Each value is called as case and the variable being switched on is checked for each case

• When we use range of values, relational operators or logical operators then we use if else.
• If we are using only values(list of values) then we go for switch case.