Answered! Determine which exception will be thrown by the Scanner class' nextInt() method. Change The CODE。 Put both of…

Determine which exception will be thrown by the Scanner class’ nextInt() method. Change The CODE。 Put both of the nextInt() calls (in my allocate2DimArray method) in a try block and catch the specific exception that nextInt() would throw if the user entered non-integer input. In the catch clause, display an error message. Use a loop to have the user to input both numbers again if an exception is caught. DON’T use recursion, but put the try block and catch clause inside a loop, using a boolean variable that will be tested in the loop condition (see example). (Optional: also catch an exception that would be thrown if the array was allocated with negative sizes)

CODE

import java.util.*;

public class Exercise4_2 {

static Scanner scanner = new Scanner(System.in);

public static void main( String [] args ){

int [][] twoDimArray;

twoDimArray = allocateTwoDimArray();

fillTwoDimArray(twoDimArray);

printTwoDimArray(twoDimArray);// not shown here

} // end main

public static int [][] allocateTwoDimArray(){

int dim1, dim2;

System.out.print(“Enter number of rows: “);

dim1 = scanner.nextInt();

if( dim1 < 1 )

dim1 = 1;

System.out.print(“Enter number of columns: “);

dim2 = scanner.nextInt();

if( dim2 < 1 )

dim2 = 1;

return new int [dim1][dim2];

} // end allocateTwoDimArray

public static void fillTwoDimArray(int [][] twoDimArray){

if( twoDimArray != null){

for( int row=0; row < twoDimArray.length; ++row ){

for( int col=0; col < twoDimArray[row].length; ++col ){

twoDimArray[row][col]=10*row+col;

} // end for col

} // end for row

}

} // end fillTwoDimArray

// print method not shown here

} // end class TryTwoDimArrays

Example:

//be sure to import java.util.* for ArrayList
ArrayList<String> list = new ArrayList<String>();
String str; int i; boolean errorOccurred;
// other code may be here
do {
          errorOccurred = false;
          try{
                    // code here to assign to i
                    str=list.get(i);// might throw an exception
                    // put code here for when there’s NO exception
          }
          catch(IndexOutOfBoundsException exp){
                    errorOccurred=true;
                    System.err.println(“Exception: ” + exp);
                    // should do more to “handle” the exception here
          } // end catch exception

}while( errorOccurred);

Expert Answer

Instead of declaring scanner as static, declare or initialise it inside your try block consisting both nextInt’s. This will avoid any infinite loops and prompt the user untill a proper valid integer input is given. Optional part in the question is not done due to time constraints but can be done similarly with the help of a try catch block and a condition to check if it is negative.

Code :

package com.geek;
import java.util.*;
public class Finaldasd {

public static void main( String [] args ){
int [][] twoDimArray;
twoDimArray = allocateTwoDimArray();
fillTwoDimArray(twoDimArray);
// printTwoDimArray(twoDimArray);// not shown here
}
public static int [][] allocateTwoDimArray(){
int dim1 = 0, dim2 = 0;
boolean first;
do{
first=false; //boolean variable to check if exception occured
//both nextInt’s in one single try catch block.
try {
//Instead of static scanner, initialize scanner in try block everytime
Scanner scanner = new Scanner(System.in);
System.out.print(“Enter number of rows: “);
dim1 = scanner.nextInt();
if( dim1 < 1 )
dim1 = 1;
System.out.print(“Enter number of columns: “);
dim2 = scanner.nextInt();
if( dim2 < 1 )
dim2 = 1;
} catch (InputMismatchException e) {
// TODO Auto-generated catch block
first=true;
System.out.println(“Enter correct format”); // prompts user again to enter valid input
}
} while(first);
return new int [dim1][dim2];
} // end allocateTwoDimArray
public static void fillTwoDimArray(int [][] twoDimArray){
if( twoDimArray != null){
for( int row=0; row < twoDimArray.length; ++row ){
for( int col=0; col < twoDimArray[row].length; ++col ){
twoDimArray[row][col]=10*row+col;
} // end for col
} // end for row
}
} // end fillTwoDimArray
// print method not shown here
} // end class TryTwoDimArrays

Output :

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