Java · Theory

Java Enums

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Theory

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Java Enums

enum defines a fixed set of named constants. Safer than int/string flags.

Can have fields and methods.

Compare with == for enum constants.

Write one tiny example for Enums. Compile, print one result, and say the output out loud before you type.

Use Enums only when the problem needs it. Don’t force it into every program. Know one beginner trap.

Let's take this on the board with one tiny Main class — no extra files. Java Enums — prints MON and true — enums are typed constants. Start from main, go line by line, and stop at each print. That output is the proof for Enums.

Exam tip

Show Day.MONDAY style usage in one line.

Example

enum Day { MON, TUE, WED }
public class Main {
  public static void main(String[] args) {
    Day d = Day.MON;
    System.out.println(d);
    System.out.println(d == Day.MON);
  }
}

Java Enums — prints MON and true — enums are typed constants.

Short notes

DefEnums is a Java idea you should explain with one small example.
RuleKnow the keyword / API used for Enums. Type a tiny Main and print one result.
RememberFor Enums, say the output before you code.
TrapEnums — only memorising the heading. No example, no trap.
Fixed constants
Type-safe

Java · Theory

Java Enums

← All stacks

Theory

65/270

Java Enums

enum defines a fixed set of named constants. Safer than int/string flags.

Can have fields and methods.

Compare with == for enum constants.

Write one tiny example for Enums. Compile, print one result, and say the output out loud before you type.

Use Enums only when the problem needs it. Don’t force it into every program. Know one beginner trap.

Exam tip

Show Day.MONDAY style usage in one line.

Example

enum Day { MON, TUE, WED }
public class Main {
  public static void main(String[] args) {
    Day d = Day.MON;
    System.out.println(d);
    System.out.println(d == Day.MON);
  }
}

Java Enums — prints MON and true — enums are typed constants.

Short notes

DefEnums is a Java idea you should explain with one small example.
RuleKnow the keyword / API used for Enums. Type a tiny Main and print one result.
RememberFor Enums, say the output before you code.
TrapEnums — only memorising the heading. No example, no trap.
Fixed constants
Type-safe

Java Enums

Example

Short notes

Questions

Java Enums

Example

Short notes

Questions