equals( )方法与 == 运算符的用法比较（(equals) compared with the operator = =.）.docVIP

equals( )方法与 == 运算符的用法比较（(equals) compared with the operator = =.） Some readers will on when to use equal operator = = and when to use the equals () method are confused, this confusion is mainly equals (...) and = = operator confusion. Although the results are sometimes the same, however, their usage is different. Take a look at the following example: Public class StringExample { Public, static, void, main (String, args[]) { String S0 = Programming; String S1 = new String (Programming); String S2 = Program + Ming; System.out.println (s0.equals (S1): + (s0.equals (S1)); System.out.println (s0.equals (S2): + (s0.equals (S2)); System.out.println (S0 = = s1: + (S0 = = S1)); System.out.println (S0 = = s2: + (S0 = = S2)); } } This example contains 3 variables of type String, two of which were assigned to a constant expression Programming is another assignment to a new value for an instance of the Programming of the String class, the use of equals (...) and = = Operators compare and produce the following results: S0.equals (S1): true S0.equals (S2): true S0 = s1: false S0 = s2: true The String.equals () method compares the content of the string, and uses the equals (...) method to compare all characters in the string one by one. If it is exactly equal, then return the true. In this case, all strings are the same, so when the string S0 is compared to S1 or S2, we get the return value of true. Operator = = is a reference to the String instance, in this case it is obvious that S0 and S1 are not the same instance of String. But S0 and S2 are the same. Maybe youll ask S0 and S2 how they are the same object? The answer to this question comes from the chapter on string constants String Literals in the Java language specification. In this example, Programming, Program and Ming are string constants. They are determined at compile time. When a string is connected by multiple string constants, such as S2, it is also determined to be a string constant at compile time. Java ensures tha