如何比較參數與Java中的對象？

有誰知道如何比較參數與對象？我一直試圖按照最後一個問題給出的說明來做：http://prntscr.com/1zaq0y但是，似乎並不是。如何比較參數與Java中的對象？

public class Classification 
    { 
     String changes; 
     String rating; 
     String description; 

    Classification() 
    { 
     rating = "G"; 
     description = "Suitable for general audiences"; 
    } 

    Classification(String must) 
    { 
     if(must != "G" || must!= "PG" || must!="M") 
     { 
      throw new NullPointerException ("Not equal"); 
     } 
     rating = must; 
     if(rating == "G") 
     { 
      description = "Suitable for general audiences"; 
     } 
     if(rating == "PG") 
     { 
      description = "Parental guidance recommended"; 
     } 
     if(rating == "M") 
     { 
      description = "Suitable for mature audiences"; 
     } 
    } 

    Classification (int num, String para) 
    { 
     if(num!= 13 || num!= 15 || num!=16 || num!=18) 
     { 
      throw new IllegalArgumentException("Not equal"); 
     } 
     if(para==null) 
     { 
      throw new NullPointerException("String is null"); 
     } 
     if(num == 16) 
     { 
      rating = "R"; 
      description = para; 
     } 
     changes = rating + num; 
    } 

    void printClassification() 
    { 
     print("Rated " + rating + ": " + description); 
    } 

    void derestrict() 
    { 
     if(rating == "M") 
     { 
      rating = "PG";  
     } 
     if(rating == "PG") 
     { 
      rating = "G"; 
     } 
     if(rating == "G") 
     { 
      throw new IllegalArgumentException("G is least restrictive"); 
     } 
     if(changes == "R18") 
     { 
      changes = "R16"; 
     } 
     if(changes == "R15") 
     { 
      changes = "R13"; 
     } 
    } 

    Classification isLessRestrictive(Classification compare) 
    { 
     if(compare==null) 
     { 
      throw new NullPointerException ("Classification para is null"); 
     } 
     if(changes<compare) 
     { 
      return true; 
     } 
     return false; 
    } 
}

來源

2013-10-23 Rob L

「參數」和「對象」之間的區別是什麼？ –

當比較String S IN的Java，你需要使用equals()。

例如，

if(must != "G" || must!= "PG" || must!="M")

應改爲

if(!"G".equals(must) || !"PG".equals(must) || !"M".equals(must))

而且

if(rating == "G")

應該是這樣的：

if("G".equals(rating))

來源

2013-10-23 23:43:41 nhgrif

不挑剔，因爲它不會影響答案，但是if（「G」.equals（rating））'更安全，因爲rating可以爲null。 – Radiodef

@Radiodef嗯，好點。我會改變答案。 – nhgrif

如何比較參數與Java中的對象？

回答

相關問題