What is the difference between the '==' operator and the equals method in Java?

The difference is as follows:

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==operator is specially used to compare two Whether the values ​​of two variables are the same, that is, used to compare whether the values ​​stored in the memory corresponding to the variables are the same. To compare two basic types of data or whether two reference variables are equal, you can only use the == operator.

The equals method is used to compare whether the contents of two independent objects are the same, just like comparing whether two books are the same. The two objects it compares are independent.

Example:

String a = new String("AA");
String b = new String("AA");
System.out.println(a==b);
System.out.println(a.equals(b));

Two new statements create two objects, and then use two variables a and b to point to one of the objects respectively. These are two different objects. They The first addresses of are different, that is, the values ​​stored in a and b are different, so the expression a==b will return false, and the contents of the two objects are the same, so a, equals(b) returns true.

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Note: String comparisons basically use the equals method.

If a class does not have its own defined equals method, then it will inherit the equals method of the Object class. The implementation code of the Object class is as follows:

boolean equals(Object o)
{
return this==o;
}

This means that if a class does not The self-defined equals method, the default equals method, is equivalent to using the == operator, that is, comparing the objects pointed to by the two variables to the same object. Use equals and == at this time.

will get the same result! ! If you want to write a class that can compare whether the contents of two instance objects are the same, you need to override the equals method!

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