Input/Output
What is prompting?
What does the following code produce?
Array[] = new int[5];
Error
Array is not a type and there is no class we can make an array of objects with.
What is the difference between error and exepction in java?
Errors are caused by the environment (JVM).
Exceptions are caused by the program itself.
What will the following code output?
for (int i = 10; i > 0; i--) {
System.out.println(i);
}
Output numbers 10-1 line by line.
What will the following code output?
int array[] = new int[] { 54, 2 };
for (int i : array) {
System.out.println(i);
}
54
2
Will the code compile?
if (true) {
break;
}
Error
Break statements can only be used with loops or switch statements.
What will the following code output?
for (int i = 0; i > 0; i++) {
System.out.println(i);
}
Nothing.
int i = 0 so the condition i > 0 is never true
What does the following code output?
int array[] = new int[] { 8, 2, 123, 2, 5, 3, 5 };
Arrays.sort(array);
for (int i : array) {
System.out.println(i);
}
2, 2, 3, 5, 5, 8, 123
Will the code compile?
public static void main(String[] args) {
FileReader reader = new FileReader("test.txt");
BufferedReader read = new BufferedReader(reader);
String line = "";
while ((line = read.readLine()) != null){
System.out.println(line);
}
reader.close();
read.close();
}
Error, no FileNotFoundException or IOException has been thrown.
What will the following code output?
System.out.println('j' + 'a' + 'v' + 'a');
Outputs 418
418 = 106 + 97 + 118 + 97
What does the following code output?
int[][] matrix = new int[][] {
{ 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 }
};
System.out.println(
matrix[matrix.length - 3][matrix.length - 2]
);
2
Will the code compile?
int array[] = new int[] { 1, 3 };
for (int i = 0; i < 3; i++) {
System.out.println(array[i]);
}
It will compile because the ArrayIndexOutOfBoundsException will occur after the program executes.
What will the following code output?
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
int value = reader.readLine();
System.out.println(value);
Error
reader.readLine() returns a String so we must convert it to an int with Integer.parseInt(reader.readLine());
What will the new matrix look like?
int[][] matrix = new int[][] {
{ 8, 4, 3 }, { 1, 12, 6 }, { 7, 8, 9 }
};
Arrays.sort(matrix, (a, b) -> a[0] - b[0]);
8 4 3
1 12 6
7 8 9
1 12 6
7 8 9
8 4 3
Is there any error with the code?
public static void main(String[] args) {
System.out.println("Num " + recursion(1));
}
public static int recursion(int num) {
if (num == 0) {
return num;
} else {
return recursion(num++);
}
}
StackOverFlow error as the recursive case never reaches its base case.