Question

In Java, the word “String” is not a keyword. That is, we can write:

String String = "";

without the compiling error.

Also, java.lang.String class can not be used as a second parameter of the “instanceof” operator.

Why? What’s so special about the String class for the Java compiler and why it isn`t a keyword?

Answer 1

First, String is a Class name, not a keyword. So you are free to use it as a variable name, although it’s not recommended.

Second, I don’t think your statement on “java.lang.String class can not be used as a second parameter of the “instanceof” operator” is correct.

I have created a test program named T2.java, it compiles and runs as expected:

import java.util.*;
import java.util.regex.*;
import java.lang.reflect.*;

public class T2 {

    public static void main(String[] args) throws Exception {
      String String = "abc";
      outputAll((String instanceof java.lang.String), String);
    }

    public static void outputAll(Object... args) {
      System.out.println();
      for (Object o: args) {
        System.out.println(o);
      }
    }

    public static void output(String msg, Object... args) {
      System.out.println(String.format(msg, args));
    }
}