Throw

 The throw keyword is used to create a custom error. It's run time exception. We use throw keyword create a user define exception and pass throw the object.

The throw statement is used together with an exception type. 

There are many exception types available in Java :  ArithmeticException , ClassNotFoundException , ArrayIndexOutOfoundException , SecurityException etc.

Syntex -
try{
throw new UserException();
}
catch(UserException e){
System.out.println("User Define Exception");
}
Example -
import java.util.*;
class UserException extends Exception{
String s=null;
UserException(int i,int j){
s=i + "is less then" + j;
}
public String toString(){
return s;
}
}
class Demo{
public static void main(String []arr){
int i,j;
Scanner sc=new Scanner(System.in);
System.out.print("Enter value of i = ");
i=sc.nextInt();
System.out.print("Enter value of j = ");
j=sc.nextInt();
if(i<j){
try{
throw new UserException(i,j);
}
catch(UserException e){
System.out.println("User Define Exception");
}
}
else{
try{
System.out.println(i/j);
}
catch(ArithmeticException e){
System.out.println("Divide By Zero");
}
}
}

}

Output -
    Enter value of i = 4
    Enter value of j = 5 
    User Define Exception
    Enter value of i = 4
    Enter value of j = 5
    1    Divide by Zero

Throws

The throws keyword indicates what exception type may be thrown by a method. The caller to these methods has to handle the exception using a try-catch block. It's exception handle in higher code. It's compiler time exception. 

There are many exception types available in Java: ArithmeticException , ClassNotFoundException , ArrayIndexOutOfoundException , SecurityException etc.

Example -
import java.io.*;
public class Throws{
 public static void main(String []arr)throws IOException{
 int i;
 i=System.in.read();
 System.out.print((char)i);
 }
}  
Output -

        Input - 456char
        Output - 4

Example -
import java.io.*;
public class Throws1{
public void display()throws IOException{
int i;
i=System.in.read();
System.out.print((char)i);
}
public static void main(String []arr)throws IOException{
Throws1 d=new Throws1();
d.display();
}
}

 Output -
        Input - char456
        Output - c