java中使用switch块代替多个if语句

Question

public class A {
  public void search(boolean[] searchList) {
    // searchList array is used to identify what options to search for in a given order
   // e.g. boolean [] searchList = new boolean [] {false, false, true, false};
    boolean searchL = false;
    boolean searchM = false;
    boolean searchK = false;
    boolean searchA = false;

    if(searchList[0] == true) searchL = true;
    if(searchList[1] == true) searchM = true;
    if(searchList[2] == true) searchK = true;
    if(searchList[3] == true) searchA = true;

    if(searchL == true) // write a query to search for all Ls
    if(searchM == true) // write a query to search for all Ms
    ...........
}

有没有办法可以简化这段代码？

@All：抱歉之前发布了错误的问题。我很困惑！

谢谢， 索尼

Answer 1

我是枚举的忠实粉丝：

public class A {
  enum SearchType {
   L, M, A, K;
 }
  public void search(SearchType type) {

    switch (type) {
     case L: 
          System.out.println("Searching for L");
          break;
     case M:
          System.out.println("Searching for M");
          break;
     case A: 
          System.out.println("Searching for A");
          break;
     case K:
          System.out.println("Searching for K");
          break;
     default:
          System.out.println("what to do here?");
          // throw exception?
}

另请注意：您的场景允许一次有多个搜索布尔值为真，我认为这不是您的目标，但如果是的话，我们可以稍微调整一下。

Answer 2

您应该将您的状态转换为枚举。例如，您的搜索布尔值似乎是排他性的，所以我会做这样的事情：

enum SearchOption {
  searchA, searchK, searchL, searchM
}

// then you can do 

SearchOption searchOption = searchA;

switch (searchOption) {
  case searchA: 
    System.out.println("I am searching for A");
    break;
  case searchK: 
    System.out.println("I am searching for K");
    break;
  case searchL: 
    System.out.println("I am searching for L");
    break;
  case searchM: 
    System.out.println("I am searching for M");
    break;    
}

如果您的状态不是排他性的，您应该尝试构建以最初构建一组排他性状态的超级集。

Answer 3

为什么不采用OOP？喜欢：

public interface Seeker {
   void seek();
}
public class LSeeker implements Seeker {
   void seek() { System.out.println("Will search for L"); }
}
// ... More implementations of Seeker
public class SeekDriver {
   void seek(Seeker seeker) { seeker.seek(); }
}

Answer 4

public class A {

    public enum SearchOption {
        SEARCH_L,
        SEARCH_M,
        SEARCH_A,
        SEARCH_K;
    }
    /**
     * Make them pass in an enum for your search.
     * Pros: type safe, can only use the selections you give
     * Cons: must add to the enum to add new types
     * @param option
     */
    public void enumSearch(SearchOption option) {

        switch(option) {
        case SEARCH_A:
            System.out.println("I am searching for A");
            break;
        case SEARCH_K:
            System.out.println("I am searching for K");
            break;
        case SEARCH_L:
            System.out.println("I am searching for L");
            break;
        case SEARCH_M:
            System.out.println("I am searching for M");
            break;
        }
    }

    /**
     * Use a primitive for your input
     * Pros: Gives you more options without updating the enum
     * Cons: Users could enter input you don't really want them to use
     * @param option
     */
    public void charSearch(char option) {
        switch(option) {
        case 'a':
        case 'A':
            System.out.println("I am searching for A");
            break;
        case 'k':
        case 'K':
            System.out.println("I am searching for K");
            break;
        case 'l':
        case 'L':
            System.out.println("I am searching for L");
            break;
        case 'm':
        case 'M':
            System.out.println("I am searching for M");
            break;
        }
    }

    /**
     * Use a primitive and don't even actually check it! Just run with it!
     * @param option
     */
    public void uncheckedSearch(char option) {
        System.out.println("I am searching for " + option);
    }
}

根据您的评论，这是我对该方法的更新示例 - 确保顶部的评论已更新！

/**
 * Perform the search based on the options provided
 * The list should be in the order of L, M, A, K
 * @note update this comment as more search options are added
 * @param searchList the list of flags indicating what to search for
 */
public void search(boolean[] searchList) {

    // as per docs, [0] denotes an L search:
    if(searchList[0]) 
        // write a query to search for all Ls

    // as per docs, [1] denotes an M search:
    if(searchList[1]) 
        // write a query to search for all Ms

    // as per docs, [2] denotes an A search:
    if(searchList[2]) 
        // write a query to search for all As

    // as per docs, [3] denotes a K search:
    if(searchList[3]) 
        // write a query to search for all Ks
}

最新想法：

// Use the SearchOption enum from above
Map<SearchOption, String> searches = new HashMap<SearchOption, String>();

public List<SearchResult> search(List<SearchOption> options) {
    List<SearchResult> results = new LinkedList<SearchResult>();
    for(SearchOption option : options) {
        String query = searches.get(option);
        SearchResult result = MySearchService.executeQuery(query);
        results.add(result);
    }
    return results;

}

Answer 5

像这样： ？

public class A {
  public void search() {

    private static final int SEARCH_L = -1;
    private static final int SEARCH_M = 0;
    private static final int SEARCH_A = 1;
    private static final int SEARCH_K = 2;

int status;

switch(status){
 case SEARCH_L:
    System.out.println("I am searching for L");
  break;
 case SEARCH_M:
    System.out.println("I am searching for M");
  break;
 // Etc

 default:
    // Log error didn't hit a known status
   break;
}

}