java语法基础

应用代码

/**
 * 类的说明
 * @author Administrator作者
 *
 */

public class hello 
{
    /**
     * 这是主方法，是程序的入口
     * @param args输入参数，字符串类型的数组
     */
    public static void main(String[] args)
    {
        //关键代码：
        //注释
        
        System.out.println("hello world");
        
        String dd123 = "";//定义变量
        
        int i;
        
        i = 123;
        
        int  m = 1,n = 2,x = 4,y = 5;
        
        
        final double  PAI = 3.14;
        
        //pai  = 3.1415926
        
        //i = "ddd";
        
        String strUserName = "tom住在这个房间里";
        
        System.out.println(strUserName);
        
        strUserName = "张三住在这里";
        
        System.out.println(strUserName);
        
        System.out.println(x);
        
        byte b = -128;
        
        short s = 2;
        
        int j = 123;
        
        int l =(int) 1234L;//强制转换，显示转换
        
        long ll = b;
        
        float f = 123.45F;
        
        double d = 123.45D;
        
        f = (float)d;
        
        f = ll;
        
        
        char c = 'a';
        
        int a = c;
        
        System.out.println("a = " + a);
        
        char g = 98;
        
        System.out.println("g = " + g);//ASCII码
        
        //UTF-8(JAVA 应用）
        
        boolean t = true; //逻辑真
        
        t = false; //逻辑假
        
        
    }

}