What are the differences between java null and empty

Generally, null in java refers to empty. But please note that there is a difference between the empty string "" and null.

"" means there is a string, but the string content is empty and the length is 0; null means the object is empty.

If you use a null object to call a method, a null pointer exception will occur.

So, when comparing string contents, you must use a non-empty string to call the comparison method.

The reference code is as follows:

public class Test {
    public static void main(String[] args) {
        String str1 = null;
        String str2 = "";
        System.out.println(str1==str2);//false
        System.out.println(str2.equals(str1));//false
        System.out.println(str1.equals(str2));//空指针异常java.lang.NullPointerException
 
    }
}

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