public class Test8 {
	public static void main(String[] args) {
		 int year, month, day;
		 String name;
	        year = 2001;
	        month = 6;
	        day = 21;
	        name = "ktt";
	        System.out.println(year + "."+ month+"."+day+"."+name);
	}
}

public class xuexiJAVA {
    public static void main(String[] args) {
        int year, month, day;
        String name;
        year = 2001;
        month = 6;
        day = 21;
        name = ktt;
        System.out.println(year + "."+ month+"."+day+"."+name);
    }
}

public static void main(String[] args) {
        int year, month, day;
        String name;
        year = 2001;
        month = 06;
        day = 07;
        name = "张三";
        System.out.println(year + "."+ month+"."+day+"."+name);
    }

public class xuexiJAVA {
    public static void main(String[] args) {
        int year, month, day, name;
        year = 2001;
        month = 6;
        day = 21;
        name ="ktt";
        System.out.println(year + "."+ month+"."+day+"."+name);
    }
}

public class xuexiJAVA {
    public static void main(String[] args) {
        int year, month, day;
        String name;
        year = 2001;
        month = 6;
        day = 21;
        name = 577;
        System.out.println(year + "."+ month+"."+day+"."+name);
    }
}

public class HelloWorld {
	public static void main(String[] args) {
		int year = 1949;
	}
}

package com.how2j;

/**
 * @author Simon.Qi
 * @version 1.0
 * @date 2020-05-20 9:56
 * @since jdk 1.8.0_191
 * 类说明：Demo演示
 */
public class Demo {
    //全部变量（类变量 用static修饰 可以直接在方法内部调用）
    static int year = 2020;

    public static void main(String[] args) {
        // 局部变量（方法内部）
        int year2 = 2020;
        System.out.println("Hello Java " + year);
        System.out.println("Hello Java " + year2);
    }
}

public class XuexiJava {
    public static void main(String[] args) {
        int year, month, day;
        string name = "ktt";
        year = 2001;
        month = 6;
        day = 21;
        System.out.println(year + "."+ month+"."+day+"."+name);
    }
}

都是可以的啊,一个是成员变量,一个局部变量
                      类中方法外为成员变量,内存位置在堆内存,
                      方法内或方法声明上就是局部变量,内存位置在栈内存

//例如
public class One{
      int c=300;  //此处为成员变量，以下main方法和two方法里都是可以使用
      public static void main(String[] args){
      int a=100;  //此处为局部变量 只能作用在main方法里面
      System.out.println(c); //此处打印变量c没有问题，因为c是成员变量
      }
      public static void two(){
      int b=200;  //此处为局部变量 只能作用在two方法里面
      //以下代码报错，因为a变量是属于main方法的变量，two方法无法使用
      //System.out.println(a)
      }
}

1949

package LEI;

public class defineYear {
	String name;
	int year;
	int mouth;
	int day;
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
			defineYear zxl = new defineYear();
			zxl.day=7;
			zxl.mouth=8;
			zxl.year =2000;
			zxl.name="朱晓龙";
			System.out.println(zxl.day);
			
	}

}

public class date {

    public static void main(String[] args) {
        int year,moth,day;

        year = 1949;
        moth = 7;
        day = 1;
        System.out.println(year + "." + moth  + "." + day);
    }

}

那么严谨，要不开场就聊虚拟机优化吧，把新手教程变成专家论文，别教啥是变量了

package jichu;

public class bianliang {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
            int a = 1;
	}

}