java syntax (11) equals(), compareTo(), == , equalsIgnoreCase() and compare()

定义

1. equals()

   • method
   • 比较两个对象的内容是否相同

2. compareTo()

   • method
   • Syntax :
     int compareTo(Object obj)
   • Parameters :
     obj : the Object to be compared.
   • Return Value :
     The value 0 if the argument is a string lexicographically equal to this string;
     a value less than 0 if the argument is a string lexicographically greater than this string;
     and a value greater than 0 if the argument is a string lexicographically less than this string.

3. ==

   • operator
   • 比较两个对象的指向的地址是否相同

4. equalsIgnoreCase()

   • Syntax : 同equals()
   • 区别：比较时忽略大小写

5. compare()

   • Syntax :
     java.text.Collator;
   • 类似compareTo()

例

    public static void main(String args[]) 
    { 
              
        String str1 = "String method tutorial";
        String str2 = "compareTo method example";
        String str3 = "string method tutorial";

        int var1 = str1.compareTo( str2 );
        System.out.println("str1 & str2 comparison: "+var1);

        int var2 = str1.compareTo( str3 );
        System.out.println("str1 & str3 comparison: "+var2);

        int var3 = str2.compareTo("compareTo method example");
        System.out.println("str2 & string argument comparison: "+var3);
        
        
        String s1 = new String("HELLO"); 
        String s2 = new String("HELLO"); 
        System.out.println(s1 == s2); 
        System.out.println(s1.equals(s2)); 
        System.out.println(s1.compareTo(s2)); 
    } 

[@参考文献]
Java | ==, equals(), compareTo(), equalsIgnoreCase() and compare()
compareTo()

作者 @FL
2019 年 04月 24日