= = and equals in Java

1,== is used to compare basic data types, and reference types. Equals is a method on an object that can be overridden by a quilt class to determine the consistency of the content.

The most wonderful is that Java basic data type (Byte,short,int,long,float,double,char,boolean), does not contain a string, so you cannot use = = to compare two strings equal.

        string S1 = new String ("abc");        String s2 = "abc";        System.out.println (S1==S2);        System.out.println (s1.equals (S2));

The result of execution is false,true.

In the habit of C # must make a mistake here, C # can be used to compare two strings equal, the advantage is not to judge whether the operands on both sides is null. Although string is not a value type in C #, it does a special deal with = =.

Like what:

        if (S1.equals ("this")) {        //mode 1        }        if ("This". Equals (S1)) {/        /mode 2        }        if (s1.equals (S2)) {        / /Mode 3        }

Both mode 1 and Mode 3 are likely to encounter null, and then the program hangs out. So generally the second way in the program is more.

But if Java also like C # to make string can be compared with = =, will bring great convenience, string class is too common.

        if (S1==S2) {        //This one is enough        }

= = and equals in Java