Question

我有一个关于天气的问题，在for循环中使用switch语句是合法的。它在Eclipse下面编写的方式给了我一个错误，并且不允许我在for循环中的第二个语句中使用switch（n）。我想做的是写...

这位老头，他打了1个他在我的拇指上玩耍诀窍。

使用for循环和switch语句是否有更好的方法解决下面的问题？我想用不同的数字和不同的情况写出不同的段落。所以1个拇指，2个鞋子，3个膝盖......直到10个。

import acm.program.*;

public class SingSong extends ConsoleProgram {

    public void run() {
        for (int n = 1; n <= 10; n++) {
            println("This old man, he played " + n);
            println("He played knick-knack on my" + switch(n));
            println("With a knick-knack, paddy-whack,");
            println("Give your dog a bone");
            println("This old man came rolling home");

            switch (n) {            
                case 1 : println("thumb"); break;
                case 2 : println("shoe"); break;
                case 3 : println("knee"); break;
                case 4 : println("door"); break;
                case 5 : println("hive"); break;
                case 6 : println("sticks"); break;
                case 7 : println("heaven"); break;
                case 8 : println ("pate"); break;
                case 9 : println("spine"); break;
                case 10 : println("shin"); break; 
            }
        } 
    }
}

Answer 1

您想要的是一种方法：

private String which(int n) {
  switch (n) {
  case 1 : return "thumb";
  case 2 : return "show";
  case 3 : return "knee";
  case 4 : return "door";
  case 5 : return "hive";
  case 6 : return "sticks";
  case 7 : return "heaven";
  case 8 : return "pate";
  case 9 : return "spine";
  case 10 : return "shin";
  default: return "";

  }
}

然后替换

println("He played knick-knack on my" + switch(n));

与

println("He played knick-knack on my" + which(n));

另一种更简洁的方法是创建一个字符串数组：

static final String[] which = {
  "thumb","show","knee","door","hive", "sticks","heaven","pate","spine","shin"};

然后只需使用

println("He played knick-knack on my" + which[n]);

Answer 2

创建一个包含整数到字符串映射的Map<Integer, String>并使用Map.get()来获取字符串：

Map<Integer, String> m = new HashMap<Integer, String>();
m.put(1, "thumb");
// etc
m.put(10, "shin");

println("He played knick-knack on my" + m.get(n));

Answer 3

    println("He played knick-knack on my" + switch(n));

这不会打电话给你的Switch。开关不是一种方法。为了获得所需的输出，

println("This old man, he played " + n);
            println("He played knick-knack on my" );

    switch (n){

            case 1 : print("thumb"); break;
            case 2 : println("shoe"); break;
            case 3 : println("knee"); break;
            case 4 : println("door"); break;
            case 5 : println("hive"); break;
            case 6 : println("sticks"); break;
            case 7 : println("heaven"); break;
            case 8 : println ("pate"); break;
            case 9 : println("spine"); break;
            case 10 : println("shin"); break; 

            }

或者更好地遵循@Marko Topolnik方法，我认为这是最好的方法。

Answer 4

SWitch（n）不是函数，不能这样使用。对于编译器来说，这就像启动一个switch语句，但完全错误，因此它返回一个错误。我认为要正确地执行此操作，您应该将case开关放在不同的方法中，或者直接放在第二行之后。像这样：

import acm.program.*;

public class SingSong extends ConsoleProgram {

public void run(){
for ( int n = 1; n <= 10; n++){

    println("This old man, he played " + n);
    print("He played knick-knack on my ");
    switch (n){
    case 1 : print("thumb"); break;
    case 2 : print("show"); break;
    case 3 : print("knee"); break;
    case 4 : print("door"); break;
    case 5 : print("hive"); break;
    case 6 : print("sticks"); break;
    case 7 : print("heaven"); break;
    case 8 : print("pate"); break;
    case 9 : print("spine"); break;
    case 10 : print("shin"); break; 
    }
    println("With a knick-knack, paddy-whack,");
    println("Give your dog a bone");
    println("This old man came roiling home");

      } 
       }

      }

这应该有效。或者用不同的方法：

 import acm.program.*;


public class SingSong extends ConsoleProgram {
public void run(){

for ( int n = 1; n <= 10; n++){

    println("This old man, he played " + n);
    print("He played knick-knack on my");
    switcher(n);
    print("\n");
    println("With a knick-knack, paddy-whack,");
    println("Give your dog a bone");
    println("This old man came roiling home");
}
}

    private void switcher(int n){
    switch(n){
    case 1 : print("thumb"); break;
    case 2 : print("show"); break;
    case 3 : print("knee"); break;
    case 4 : print("door"); break;
    case 5 : print("hive"); break;
    case 6 : print("sticks"); break;
    case 7 : print("heaven"); break;
    case 8 : print ("pate"); break;
    case 9 : print("spine"); break;
    case 10 : print("shin"); break; 


      } 
       }

      }

Answer 5

使用if-else代替switch语句。

if(n==1){
 ...
}else if(n==2){
 ...
}

Answer 6

你不能这样做：

println("He played knick-knack on my" + switch(n));

如果您希望代码大致相同，则应委托执行切换的方法。

替代解决方案将包括if / else if（有点冗长）的序列，或者可能是充当查找表的数组。

e.g。

// note arrays are indexed from 0
String[] arrayOfObjects = new String[]{"thumb", ....};
println("He played knick-knack on my" + arrayOfObjects(n-1));

我认为，除非你有非连续的索引（不太可能），否则Map在这种情况下可能有点过分

Answer 7

您正在使用switch方法。做以下更改，它将起作用：

import acm.program.*;

public class SingSong extends ConsoleProgram 
{
    public void run()
    {
        for ( int n = 1; n <= 10; n++)
        {
            println("This old man, he played " + n);
            println("He played knick-knack on my" + getValue(n));
            println("With a knick-knack, paddy-whack,");
            println("Give your dog a bone");
            println("This old man came roiling home");
        }
    }

    private String getValue(int n)
    {
        switch (n)
        {
            case 1 : return "thumb"; break;
            case 2 : return "shoe"; break;
            case 3 : return "knee"; break;
            case 4 : return "door"; break;
            case 5 : return "hive"; break;
            case 6 : return "sticks"; break;
            case 7 : return "heaven"; break;
            case 8 : return "pate"; break;
            case 9 : return "spine"; break;
            case 10 : return "shin"; break;

            default : return "VALUE NOT FOUND!!";
        }
    } 
}

Answer 8

for循环中的switch / case语句很好，问题是switch不是函数调用。尝试这样的事情：

    string obj;
    switch (n){

    case 1 : obj="thumb"; break;
    case 2 : obj="show"; break;
    //Etc
    }


    }
    println("This old man, he played " + n);
    println("He played knick-knack on my" + obj);
    println("With a knick-knack, paddy-whack,");
    println("Give your dog a bone");
    println("This old man came roiling home");

在for循环中使用switch语句

8 个答案: