| 1 | int total = 0
total = total + 45; | ';' expected | int total = 0; Every statement ends with a semicolon |
| 2 | int runs = 64;
system.out.println(runs); | package system does not exist | System.out.println(runs); Java is case sensitive; System is a class with a capital S |
| 3 | String city = 'Pune'; | unclosed character literal | String city = "Pune"; Single quotes hold exactly one char; Strings need double quotes |
| 4 | int weight = 52.5; | incompatible types: possible lossy conversion from double to int | double weight = 52.5; A decimal literal is a double and cannot be squeezed into an int without a cast |
| 5 | int points;
points = points + 10; | variable points might not have been initialized | int points = 0; Local variables get no default value |
| 6 | int age = 15;
if (age = 15)
System.out.println("Class 10"); | incompatible types: int cannot be converted to boolean | if (age == 15) One = assigns; == compares |
| 7 | static int cube(int n) {
int c = n * n * n;
} | missing return statement | Add return c; before the closing brace; a method declared int must return an int |
| 8 | char grade = "A"; | incompatible types: String cannot be converted to char | char grade = 'A'; Double quotes make a String even for one letter |
| 9 | void greet() { ... }
// inside static main:
greet(); | non-static method greet() cannot be referenced from a static context | Declare it static void greet(), or call it through an object of the class |
| 10 | for (int k = 1; k <= 5; k++) {
System.out.print(k);
}
System.out.println(k); | cannot find symbol (symbol: variable k) | Declare int k; before the loop and write for (k = 1; k <= 5; k++). A variable declared in the for header dies when the loop ends |
| 11 | int score = 70;
int score = 85; | variable score is already defined in method main(String[]) | score = 85; Declare once, assign as often as you like |
| 12 | if (x > 5)
System.out.println("big");
System.out.println("checked");
else
System.out.println("small"); | 'else' without 'if' | Put the two println lines inside { }. Without braces the if owns only one statement |
| 13 | String word = "BlueJ";
System.out.println(word.length); | cannot find symbol (symbol: variable length) | word.length() For a String, length is a method |
| 14 | int[] marks = {80, 75, 91};
System.out.println(marks.length()); | cannot find symbol (symbol: method length()) | marks.length For an array, length is a field, no brackets |
| 15 | int r = Math.round(4.6); | incompatible types: possible lossy conversion from long to int | long r = Math.round(4.6); or int r = (int) Math.round(4.6); round of a double returns long |
| 16 | switch (day) {
case 1: ... break;
case 2: ... break;
case 2: ... break;
} | duplicate case label | Change the third label to case 3: Each case value may appear once |
| 17 | static void area(int s) {
return s * s;
} | incompatible types: unexpected return value | static int area(int s) A void method cannot hand back a value |
| 18 | while (n > 0) {
n--;
break;
System.out.println(n);
} | unreachable statement | Move the println above the break, or delete it. Java refuses code that can never run |
| 19 | boolean pass = 1; | incompatible types: int cannot be converted to boolean | boolean pass = true; Java booleans are only true and false, never 0 or 1 |
| 20 | float rate = 7.5; | incompatible types: possible lossy conversion from double to float | float rate = 7.5f; A literal with a decimal point is double unless it carries f |
