Hello.java——java语法基础的应用 续

  1 /**
  2  * 类的说明
  3  * 
  4  * @author hasee作者
  5  *
  6  */
  7 public class hello {
  8     /**
  9      * 这是主方法，是程序的入口
 10      * 
 11      * @param args输入参数，字符串类型的数组
 12      */
 13     public static void main(String[] args) {
 14         // 关键代码
 15         // 注释
 16 
 17         System.out.println("Hello World");
 18 
 19         String _$dd123 = "";// 定义变量
 20 
 21         int i;
 22 
 23         i = 123;
 24 
 25         int m = 1, n = 2, x = 4, y = 5;
 26 
 27         final double PAI = 3.14;
 28 
 29         // pai = 3.1415926;
 30 
 31         // i = "ddd"
 32 
 33         String strUserName = "tom住在这个房间";
 34 
 35         System.out.println(strUserName);
 36 
 37         strUserName = "张三住在这里";
 38 
 39         System.out.println(strUserName);
 40 
 41         byte b = -128;
 42 
 43         short s = 2;
 44 
 45         int j = 123;
 46 
 47         int l = (int) 1234L;// 强制转换，显示转换
 48 
 49         long ll = b;
 50 
 51         float f = 123.45F;
 52 
 53         double d = 123.45D;
 54 
 55         f = (float) d;
 56 
 57         char c = ‘a‘;
 58 
 59         int a = c;
 60 
 61         System.out.println("a =" + a);
 62 
 63         char g = 98;
 64 
 65         System.out.println("g =" + g); // ASCII码
 66 
 67         // UTF-8
 68 
 69         boolean t = true;// 1表示true，逻辑真
 70 
 71         t = false;// 0表示false，逻辑假
 72 
 73         System.out.println("20 % 7 = " + (20 % 7));
 74 
 75         int z = 10;
 76 
 77         // z++; //z = z + 1
 78 
 79         System.out.println("z = " + z++);
 80 
 81         // z--; //z = z - 1
 82 
 83         System.out.println("z = " + z--);
 84 
 85         System.out.println("z = " + z);
 86 
 87         // System.out.println("z = " + ++z);
 88 
 89         // z--; //z = z - 1
 90 
 91         // System.out.println("z = " + --z);
 92 
 93         // System.out.println("z = " + z);
 94 
 95         z = 10;
 96 
 97         int k = ++z;
 98 
 99         z += 2;// z = z+2;
100         z -= 2;// z = z-2;
101 
102         z *= 2;// z = z *2;
103         z /= 2;// z = z /2;
104         z %= 2;// z = z %2;
105 
106         boolean luoji = true & true;
107         System.out.println("true && true = " + luoji);
108 
109         luoji = true && false;
110         System.out.println("true && false = " + luoji);
111 
112         luoji = false && false;
113         System.out.println("false && false = " + luoji);
114 
115         luoji = (2 > 1 & 3 < 4);
116 
117         luoji = true || true;
118         System.out.println("true ||  true = " + luoji);
119 
120         luoji = true || false;
121         System.out.println("true || false = " + luoji);
122 
123         luoji = false || false;
124         System.out.println("false || false = " + luoji);
125 
126         luoji = !(2 > 1 || 3 > 4);// 本来结果为true，前面加了！结果就反转了成了false
127 
128         int v = 2 > 1 ? 1 : 2;
129 
130         String str = 4 > 5 ? "asd" : "";
131 
132         String ss = "";
133 
134         if (4 > 5) {
135             ss = "asd";
136         }
137 
138         int q = ((2 + 1) * (4 - 3));
139 
140         System.out.println("10 != 9 = " + (10 == 9));
141 
142         String a2 = "";
143 
144     }
145 }