values and valueOf

Learn enum operations with values() and valueOf().

values returns all constants

values() returns all constants of an enum as an array. valueOf(String) obtains a constant from a name. These are the core tools for looping and conversion.

for (Day d : Day.values()) {
  System.out.println(d);
}
Day d = Day.valueOf("MONDAY");

values() creates a new array on each call, but for small enums this does not matter. valueOf throws IllegalArgumentException if the name is not found, so you should validate input. Together they make it easy to iterate over an enum.

Iterate constants with for-each

The array returned by values() makes a for-each loop easy to write. This is the most common way to list all options of an enum.

for (Day d : Day.values()) {
  System.out.println(d + " " + d.ordinal());
}

The loop order matches the declaration order, so the output is predictable. This pattern is very handy for listing menu options or processing all states. You can also access the ordinal with ordinal().

Exercise List all days

Define the Day enum (MONDAY through SUNDAY). Build a for-each loop over values() and print each day on its own line.

Show example solution

enum Day { MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY }
// inside main:
for (Day d : Day.values()) {
  System.out.println(d);
}

Test yourself

What does Day.valueOf("MONDAY") return?
- An array
- The string "MONDAY"
- 0
- The Day.MONDAY constant
Show answer

The Day.MONDAY constant — valueOf obtains an enum constant from a name; it returns the constant itself, not a string.
Match each method to its return type

values()

Day[]
valueOf(String)

Day
ordinal()

int
name()

String

Find a constant with valueOf

Day d = Day.____("MONDAY");

Show answer

Day d = Day.valueOf("MONDAY");

Next lesson: Enum fields

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