2. Predefined
method:
If a method is already defined by
programmer in java library
Examples:
- Math.min()
- Math.max()
- Math.sqrt()
min()
{
}
Math
Class:
- The Math class in Java is a
predefined class.
- It contains methods to
perform mathematical operations.
Common
Methods:
- Math.min(): Returns the smaller of two
values.
- Math.max(): Returns the larger of two
values.
- Math.sqrt(): Returns the square root of
a value.
Tips for Exploring Predefined Methods:
- Viewing Method Implementations:
- Tip 1: To view the code
of a predefined method, press
Ctrland move the mouse over the method name (e.g.,max()) and click "Open Declaration". - This
will navigate to the method's body in the Java library, allowing you to
see its implementation.
- Searching for Methods:
- Tip 2: To view all
methods in a class, use
Ctrl + O(the letter 'O') to open the outline view. - You
can also search for specific method names, such as
min, to quickly locate them within the class.
package PreDefinedMethods;
public class MathBasicsMethods {
public
static void main(String[] args) {
//
call max
int
maxValue = Math.max(2, 5);
// max() ;; max no = 5
// maxValue = 5
System.out.println("result
max="+maxValue);
// 5
//
Min () - pass 2,5
int
minVal = Math.min(2, 5);
// 2
//
// minVal= 2
System.out.println("minVal="+minVal);
// 2
//
sqaure root of no -pass 4.0 --> 2.0
double sqrtResult=
Math.sqrt(4.0);
// 2.0
/// sqrtResult = 2.0
// 2.0
System.out.println("sqrtResult="+sqrtResult);
// int no=
Math.sqrt(4.0);// error :Type mismatch: cannot convert from double to int
//
sqrt() return double value
but left we declared int
var..
// so we should declare double variable left
side
//
Tip: how to know method return type
: move mouse over on method name-- left side some data type
// HW call ,max () by passing float values
//HW call ,min () by passing float values
}
}
HW WAP to Define a Method to
Square a Given Number and Pass an Integer
squareNo(2); o/p ://4
2 * 2 = 4
3 * 3 = 9
return n*n; // this
also fine
HW WAP to define method -square given no and pass float no
square (2.0) // 4.0
HW WAP to define method -cube of given no and pass- int no
2 *2 *2 = 8
3*3*3 = 27
HW WAP to define method - cube of given no and pass- float no
2.0 * 2.0 *2.0 = 8.0
Return type Casting:
package PreDefinedMethods;
public class ReturnTypCasting
{
public
static float add(int a, int b)
{// 2 3 so a =2 , b =3
int
res= a+b;
// 2 + 3
// 5
// int
res= 5
return
res;// returning int val
// return 5;
returning int value ---> this val will be typacsted/ converted to
float val
// 5 --> 5.0 returns float val but not int val.
}
public
static void main(String[] args)
{
// call add() pass 2,3
float
result = add(2,3);
// 5.0
// result = 5.0
// but not 5
//
Display the o/p
System.out.println("result
="+result);
//
val 5.0
}
}
o/p:
result =5.0
package PreDefinedMethods;
public class AddMethodWith2args {
//
public
static int add(int a, int b)
{
// 2 3
// a=2 b =3
float
res= a+b;
// 2 + 3
// 5
// float
res= 5 // Implicit
type casting
// conver int --> float
// 5 --> 5.0
// res
= 5.0
System.out.println("res="+res);//
// 5.0
// return
res;// type mismatch: cannot
convert from float to int
// 5.0
return
(int)res;
// 5.0 --> 5 ----->
this method gives o/p = 5
}
public
static void main(String[] args)
{
int
val= add(2,3);
// 5
// val = 5
System.out.println("val
="+val);
// val =5
}
}
o/p:
res=5.0
val =5
note:
void squareGivenNoNew(4)
{
// dont write return stmt inside method
}
// void v=
squareGivenNoNew(4);// invalid don’t use
like this
void method -- cannot return any val/ won’t give o/p
int a =
squareGivenNoNew(4);// CE:
Note2:
package PreDefinedMethods;
public class SquareGivenNo2 {
//
Define -squareGivenNo() pass int
arg and return type -void
public
static void squareGivenNo (int n)
{
// 2*2 = 4 2 so n= 2
//
3*3 = 9
// n * n --
square no
int
result = n*n;
// 2*2
// 4
//result =4
System.out.println("result-"+
result);
// 4
}
public
static void main(String[] args)
{
// int sqr =
squareGivenNo(3);//Error: Type mismatch: cannot convert from void to int
//
error : gives nothing as method
return type is void
// We cannot store result into some variable
// System.out.println("sqr="+sqr);
squareGivenNo(2);
// void v = squareGivenNo(2); //Error:void is an
invalid type for the variable v
}
}
Method returns array:
By using
a method, we can return:
- int value or int variable
- float value or float
variable
- char value or char variable
- String value or String
variable
- Array variable name (to
return a group of values)
Invalid
examples:
- return 10,20,30; // invalid
- return a,b,c; // invalid
return val/ var/ expression;
Valid
examples:
- return val; // where val is a single
value
- return var; // where var is a single
variable
- return expression; // where expression
evaluates to a single value
Syntax:
return arrayName;
ex:
package PreDefinedMethods;
public class
MethodReturnsIntArray {
//define
M1() Method return int array
//
method return type int[] - int array
public
static int[] M1()
{
int
a ;
int
[] iarr = new int [3];
iarr
[0] = 10;
iarr
[1] = 20;
iarr
[2] = 30;
// return arrayName;
return
iarr; // ---->> gives o/p int array [10,20,30]
// return a;//Error: Method return type is
int array i.e int [] . so we must return int array only but not int value
//
Type mismatch: cannot convert from int[] to int
// [10,20,30]
}
public
static void main(String[] args) {
//
call M1()
int
[] arr = M1();
// [10,20,30]
// arr
= [10,20,30]
// 0
1 2
//
display array values
for(int
i=0;i<=arr.length-1;i++)
{
System.out.println("values
from array="+ arr[i]);
}
}
}
o/p:
values from array=10
values from array=20
values from array=30
//
Ex
// public static float[]
display()
// char []
// boolean []
{
// floar
farr[]
// char charr[]
// boolean barr[]
return
farr;
}
HW WAP to Define method and return float array and display array values in main()
HW WAP to Define method and return char array and display array values in main()
HW WAP to Define method and return String array and display array values in main()
No comments:
Post a Comment