Describe Java class variables, member variables, and local variables in an instance

There are generally three variables in Java: Class variables, member variables, and local variables. class variables

1. Let's look at the following example for a class variable

public class demo6{public    String name;    public int age;    public static String sex= "male";    Public Demo6 (String name, int age) {        this.name = name;        This.age = age;;    }    public void Say () {        System.out.println ("My Name is" +name+ ", I Am" +age+ "year old.");    public static void Main (String args[]) {        Demo6 obj = new Demo6 ("Alex");        Obj.say ();        System.out.println ("I Am" +sex+ "health");//        System.out.println ("I Am" +age+ "year old");}    }

Class variables can be accessed without instantiation (PS: If an instance changes the value of a class variable, the other instance calls the value of such a variable)

If you remove the comment

System.out.println ("I" +age+ "year");

, you will get an error: Error: (+) Java:/users/lsf/ideaprojects/javapractice/src/demo6.java:19: Cannot reference a non-static variable from a static context

2. Next look at the member variables and local variables, or look at this example, make a little change

public class demo6{public    String name;    public int age;    public static String sex= "male";    Public Demo6 (String name1, int.) {        this.name = name1;        This.age = age;;    }    public void Say () {        System.out.println ("My Name is" +name+ ", I Am" +age+ "year old.); /        System.out.println ("My name is +name1+", I'm "+age+" this year);    }    public static void Main (String args[]) {        Demo6 obj = new Demo6 ("Alex");        Obj.say ();        System.out.println ("I Am" +sex+ ");}    }

The result is correct when you execute the following sentence:

System.out.println ("My name is +name+", I Am "+age+" this year);

This is because name is a member variable and is valid throughout the instance. And name1 is a local variable, only valid in the method body, if you call name1 as follows, you will get an error

System.out.println ("My name is +name1+", I Am "+age+" this year);

The error message is:

Error: (+) Java: no symbols found
Symbol: Variable name1
Location: Class Demo6

Describe Java class variables, member variables, and local variables in an instance