void在Java中做什么?
返回类型-方法返回的值的数据类型;如果该方法未返回值,则返回void。
http://download.oracle.com/javase/tutorial/java/javaOO/methods.html
那好吧..这是我的问题:
public class EnumTest { Day day;
public EnumTest(Day day) {
this.day = day;
}
public void tellItLikeItIs() {
switch (day) {
case MONDAY: System.out.println("Mondays are bad.");
break;
case FRIDAY: System.out.println("Fridays are better.");
break;
case SATURDAY:
case SUNDAY: System.out.println("Weekends are best.");
break;
default: System.out.println("Midweek days are so-so.");
break;
}
}
public static void main(String[] args) {
EnumTest firstDay = new EnumTest(Day.MONDAY);
firstDay.tellItLikeItIs();
EnumTest thirdDay = new EnumTest(Day.WEDNESDAY);
thirdDay.tellItLikeItIs();
EnumTest fifthDay = new EnumTest(Day.FRIDAY);
fifthDay.tellItLikeItIs();
EnumTest sixthDay = new EnumTest(Day.SATURDAY);
sixthDay.tellItLikeItIs();
EnumTest seventhDay = new EnumTest(Day.SUNDAY);
seventhDay.tellItLikeItIs();
}
}
http://download.oracle.com/javase/tutorial/java/javaOO/enum.html
上面的代码没有无效就无法工作。
Exception in thread "main" java.lang.Error: Unresolved compilation problems: The method tellItLikeItIs() is undefined for the type EnumTest
我错过了什么?为什么那里有空隙?并返回字符串吗?
回答:
代码无法运行的原因void
是因为该System.out.println(String
string)方法不返回任何内容,仅将提供的参数打印到标准输出终端(在大多数情况下为计算机监视器)。当方法返回“
nothing”时,您必须通过将void
关键字置于其签名中来进行指定。
您可以在此处查看System.out.println的文档:
http://download.oracle.com/javase/6/docs/api/java/io/PrintStream.html#println%28java.lang.String%29
为了进一步解决这个问题,println是将计算作为“副作用”执行的方法的经典示例。
以上是 void在Java中做什么? 的全部内容, 来源链接: utcz.com/qa/417818.html