close
一般定義常數方式如下：
public class Robot {
public static final int COMMAND_WALK = 0;
public static final int COMMAND_STOP = 1;
public static final int COMMAND_JUMP = 2;
}
比較時是使用int為input參數：
public void order (int command) {
if (command == COMMAND_WALK) {
} else if (command == COMMAND_STOP) {
} else if (command == COMMAND_JUMP) {
} else {
}
}
以下是JDK 1.4以下用Class的替代方案：
public class RobotCommand {
private final String _name;
public RobotCommand (String name) { _name=name; }
public String toString() { return "[RobotCommand: " + _name + "]"; }
}
比較時是使用RobotCommand 為input參數：
public static final RobotCommand COMMAND_WALK = new RobotCommand("WALK");
public static final RobotCommand COMMAND_STOP = new RobotCommand("STOP");
public static final RobotCommand COMMAND_JUMP = new RobotCommand("JUMP");
public void order (RobotCommand command) {
if (command == COMMAND_WALK) {
} else if (command == COMMAND_STOP) {
} else if (command == COMMAND_JUMP) {
} else {
}
}
以下是JDK 5.0以上用Enum的替代方案：
public class Robot {
public enum Command {
WALK,
STOP,
JUMP,
};
}
比較時是使用Robot.Command 為input參數：(outter.inner)
public void order (Robot.Command command) {
if (command == Robot.Command.WALK) {
} else if (command == Robot.Command.STOP) {
} else if (command == Robot.Command.JUMP) {
} else {
}
}
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