equals（）方法？

Question

shouldn´t one pass an object to equal?

    String hej = pets.getBark();
    if(hej.equals("woff"))

why are you able to pass a string woff?

Answer 1

If I understand your question properly you are wondering why a literal string value can be passed to a method that accepts an argument of type String . This is because a string literal is a shorthand for a String instance (either a new instance or a previously created instance that has been preserved by means of interning):

The String class represents character strings. All string literals in Java programs, such as "abc", are implemented as instances of this class.

Answer 2

A quoted string is an object. It is an instance of the String class.

Answer 3

Under the hood, a string literal ( text inside quotes ) automatically is replaced by String instance. ( a string literal is shorthand for new String )

That is why this code works: String hello = "hello";

So,

 String hej = pets.getBark();
 if( hej.equals( new String("woff") ) ) {}

is identical to the code you provided.

Answer 4

您可以传递java.lang.String的子类型java.lang.Object ，因为Liskov替换原理如此。

Answer 5

文字字符串仍为String类型。