James Curran简洁地说:“基于整数的开关可以优化为非常高效的代码。基于其他数据类型的开关只能编译为一系列if()语句。因此，C和c++只允许在整数类型上切换，因为这对其他类型是没有意义的。”

My opinion, and it's only that, is that as soon as you start switching on non-primitives you need to start thinking about "equals" versus "==". Firstly comparing two strings can be a fairly lengthy procedure, adding to the performance problems that are mentioned above. Secondly if there is switching on strings there will be demand for switching on strings ignoring case, switching on strings considering/ignoring locale,switching on strings based on regex.... I would approve of a decision that saved a lot of time for the language developers at the cost of a small amount of time for programmers.

不是很漂亮，但这里是Java 6的另一种方式:

String runFct = 
        queryType.equals("eq") ? "method1":
        queryType.equals("L_L")? "method2":
        queryType.equals("L_R")? "method3":
        queryType.equals("L_LR")? "method4":
            "method5";
Method m = this.getClass().getMethod(runFct);
m.invoke(this);

如果您没有使用JDK7或更高版本，可以使用hashCode()来模拟它。因为String.hashCode()通常为不同的字符串返回不同的值，并且总是为相同的字符串返回相同的值，所以它是相当可靠的(不同的字符串可以产生与评论中提到的@Lii相同的哈希代码，例如“FB”和“Ea”)。

所以，代码看起来是这样的:

String s = "<Your String>";

switch(s.hashCode()) {
case "Hello".hashCode(): break;
case "Goodbye".hashCode(): break;
}

这样，你在技术上开启了一个整型。

或者，你可以使用下面的代码:

public final class Switch<T> {
    private final HashMap<T, Runnable> cases = new HashMap<T, Runnable>(0);

    public void addCase(T object, Runnable action) {
        this.cases.put(object, action);
    }

    public void SWITCH(T object) {
        for (T t : this.cases.keySet()) {
            if (object.equals(t)) { // This means that the class works with any object!
                this.cases.get(t).run();
                break;
            }
        }
    }
}

在Java 11+中，变量也是可行的。唯一的条件是它必须是常数。

例如:

final String LEFT = "left";
final String RIGHT = "right";
final String UP = "up";
final String DOWN = "down";

String var = ...;

switch (var) {
    case LEFT:
    case RIGHT:
    case DOWN:
    default:
        return 0;
}

PS.我还没有在早期的jdk中尝试过这一点。所以请更新答案，如果它也支持。

下面是一个基于JeeBee的帖子的完整示例，使用java枚举而不是使用自定义方法。

注意，在Java SE 7及更高版本中，您可以在switch语句的表达式中使用String对象。

public class Main {

    /**
    * @param args the command line arguments
    */
    public static void main(String[] args) {

      String current = args[0];
      Days currentDay = Days.valueOf(current.toUpperCase());

      switch (currentDay) {
          case MONDAY:
          case TUESDAY:
          case WEDNESDAY:
              System.out.println("boring");
              break;
          case THURSDAY:
              System.out.println("getting better");
          case FRIDAY:
          case SATURDAY:
          case SUNDAY:
              System.out.println("much better");
              break;

      }
  }

  public enum Days {

    MONDAY,
    TUESDAY,
    WEDNESDAY,
    THURSDAY,
    FRIDAY,
    SATURDAY,
    SUNDAY
  }
}

从1.7开始直接使用String的例子如下:

public static void main(String[] args) {

    switch (args[0]) {
        case "Monday":
        case "Tuesday":
        case "Wednesday":
            System.out.println("boring");
            break;
        case "Thursday":
            System.out.println("getting better");
        case "Friday":
        case "Saturday":
        case "Sunday":
            System.out.println("much better");
            break;
    }

}