How Does the Java 7 Switch Statement Work with Strings?

How does the switch statement in Java 7 handle String comparisons? Does it use the equals() method or rely on == for its operations?

switch (month.toLowerCase()) {
case "january":
    monthNumber = 1;
    break;
case "february":
    monthNumber = 2;
    break;
default:
    monthNumber = 0;
    break;
}

The Java 7 switch statement allows for the direct use of String objects in switch expressions. This enhances clarity and readability, particularly in cases where multiple conditions need to be evaluated.

String month = month.toLowerCase();
if("january".equals(month)) {
    monthNumber = 1;
} else if("february".equals(month)) {
    monthNumber = 2;
} else {
    monthNumber = 0;
}

Causes

• The Java switch statement performs comparisons between the String in the switch expression and the case labels using the equals() method.
• Using String in a switch leverages the internal mechanisms of Java Objects to ensure proper comparison of String values.

Solutions

• As provided by the Java Documentation, the switch expression compares the String values as if the equals() method were explicitly invoked.
• For optimized performance in scenarios with numerous branches, ensure that your case labels are constant expressions.

Mistake: Using == to compare Strings within a switch case.

Solution: Always use .equals() for String comparison, as == checks for reference equality, not content equality.

Mistake: Assuming that switch statements prevent NullPointerExceptions.

Solution: Always validate your Strings before passing them to a switch statement.