Conditionals and Loops

Programs rarely run in a straight line. You often need to make decisions or repeat some code. In Java you use conditionals and loops for this.

if and else

java
int score = 75;
if (score >= 70) {
    System.out.println(\"Passed\");
} else {
    System.out.println(\"Failed\");
}

else if

java
if (score >= 90) {
    System.out.println(\"Excellent\");
} else if (score >= 70) {
    System.out.println(\"Good\");
} else {
    System.out.println(\"Needs improvement\");
}

switch

java
int day = 3;
switch (day) {
    case 1 -> System.out.println(\"Monday\");
    case 2 -> System.out.println(\"Tuesday\");
    default -> System.out.println(\"Other day\");
}

for loop

java
for (int i = 0; i < 5; i++) {
    System.out.println(\"i = \" + i);
}

while loop

java
int j = 0;
while (j < 3) {
    System.out.println(j);
    j++;
}

In the next lesson you will see how to group behaviour into reusable methods.