This is your solution. I know there are lots of if else
statements but this is my best.
for(int i=0;i<a.length;i++){
for(int j=0;j<a[i].length;j++){
if(i==0){
if(j==0){
sum[i][j] = a[i][j]*2 + a[i+1][j] + a[i][j+1];
}
else if(j==a[i].length-1){
sum[i][j] = a[i][j]*2 + a[i][j-1] + a[i+1][j] ;
}
else{
sum[i][j] = a[i][j] + a[i][j-1] + a[i+1][j] + a[i][j+1];
}
}
else if(i==a.length-1){
if(j==0){
sum[i][j] = a[i][j]*2 + a[i-1][j] + a[i][j+1];
}
else if(j==a[i].length-1){
sum[i][j] = a[i][j]*2 + a[i][j-1] + a[i-1][j] ;
}
else{
sum[i][j] = a[i][j] + a[i][j-1] + a[i-1][j] + a[i][j+1];
}
}
else if(j==0){
sum[i][j] = a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j+1];
}
else if(j==a[i].length-1){
sum[i][j] = a[i][j] + a[i-1][j] + a[i+1][j] + a[i][j-1];
}
else{
sum[i][j] = a[i][j-1] + a[i-1][j] + a[i+1][j] + a[i][j+1];
}
}
}