In this program, you'll learn to find the largest among three numbers using if else and nested if..else statement in Java.

```
public class Largest {
public static void main(String[] args) {
double n1 = -4.5, n2 = 3.9, n3 = 2.5;
if( n1 >= n2 && n1 >= n3)
System.out.println(n1 + " is the largest number.");
else if (n2 >= n1 && n2 >= n3)
System.out.println(n2 + " is the largest number.");
else
System.out.println(n3 + " is the largest number.");
}
}
```

When you run the program, the output will be:

3.9 is the largest number.

In the above program, three numbers `-4.5`

, `3.9`

and `2.5`

are stored in variables `n1`, `n2` and `n3` respectively.

Then, to find the largest, the following conditions are checked using if else statements

- If
`n1`is greater or equals to both`n2`and`n3`,`n1`is the greatest. - If
`n2`is greater or equals to both`n1`and`n3`,`n2`is the greatest. - Else,
`n3`is the greatest.

The greatest number can also be found using a nested if..else statement.

```
public class Largest {
public static void main(String[] args) {
double n1 = -4.5, n2 = 3.9, n3 = 5.5;
if(n1 >= n2) {
if(n1 >= n3)
System.out.println(n1 + " is the largest number.");
else
System.out.println(n3 + " is the largest number.");
} else {
if(n2 >= n3)
System.out.println(n2 + " is the largest number.");
else
System.out.println(n3 + " is the largest number.");
}
}
}
```

When you run the program, the output will be:

5.5 is the largest number.

In the above program, instead of checking for two conditions in a single if statement, we use nested if to find the greatest.

Then, to find the largest, the following conditions are checked using if else statements

- If
`n1`is greater or equals to`n2,`- and if
`n1`is greater or equals to`n3`,`n1`is the greatest. - else,
`n3`is the greatest.

- and if
- Else,
- if
`n2`is greater or equals to both`n3`,`n2`is the greatest. - else,
`n3`is the greatest.

- if