Desplegar diagonal en una matriz

import java.util.*;
public class diagonal{
   public static void main (){
       int a[][] = new int [5][5];
       int num,i,j;
       Scanner teclado = new Scanner (System.in);
       System.out.println("Escribe el numero de la diagonal");
       num = teclado.nextInt();
       for (i=0;i<=4;i++){
           for (j=0;j<=4;j++){
               if (i==j){
                   a[i][j]=num;
                }
                else {
                    a[i][j]=0;
                }
            }
        }
        for (i=0;i<4;i++){
           for (j=0;j<4;j++){
               System.out.print(a[i][j]+"|");
               }
        System.out.println("");
          }
        }
    }