java入门程序

public class Test { public static void main(String[] args) { // 方法的开始大括弧 /* byte b = 10; // byte b1 = 128; short s = 20; // short s1 = 65536; int i = 30; long l = 10; long l1 = 2147483647; long l2 = 2147483648L;//超过int范围需要加l或L float f = 10.2f;//浮点数默认是double，直接赋值编译错误 double d = 10.2; // 转义字符 char c = 'a'; char c1 = '\''; char c2 = '"'; char c3 = '\\'; System.out.println(c1); System.out.println(c2); System.out.println(c3); System.out.print("abc"); System.out.print("\r");// 回车 System.out.print("ef"); System.out.print("\n");// 换行 System.out.print("gh"); System.out.print("\u000F"); // boolean类型 boolean b1 = true; boolean b2 = false; */ // 位运算 int i = 10; byte j = 10; System.out.println(i); System.out.println(i&20); //System.out.println(!j); System.out.println(i|20); System.out.println(i^20); // 移位操作 byte a; a = 127; /* a左移2位 01111111 00000000 00000000 00000000 01111111 000000 00000000 00000000 0111111100 ----508 */ int d = a << 2; System.out.println(d); /* -127原码 10000000 00000000 00000000 01111111 反码 11111111 11111111 11111111 10000000 补码 11111111 11111111 11111111 10000001 有符号右移2位 11111111 11111111 11111111 11100000 反码 11111111 11111111 11111111 11011111 原码10000000 00000000 00000000 00100000 -32 */ a = -127; d = a >> 2; System.out.println(d); /* -127原码 10000000 00000000 00000000 01111111 反码 11111111 11111111 11111111 10000000 补码 11111111 11111111 11111111 10000001 无符号右移2位 00111111 11111111 11111111 11100000 1073741792 */ a = -127; d = a >>> 2; System.out.println(d); short s = -489; int g = s<<4; System.out.println(g); g=s>>4; System.out.println(g); g=s>>>4; System.out.println(g); // 类型转换 // 自动类型转换 byte age = 10; short sage = age; int iage = sage; iage = age; char c = 'a'; iage = c; System.out.println(iage); double d2 = age; System.out.println(d2); float f2 = 1.23f; d2 = f2; // 强制类型转换 int ii = 12; byte bb = (byte)ii; /* 150 : 00000000 00000000 00000000 10010110 10010110 11101010 -106 */ int ii2 = 150; byte bb2 = (byte)ii2; System.out.println(bb2); double dd = 12.4; ii2 = (int)dd; System.out.println(ii2); int ii3 = 98; char cc1 = (char)ii3; System.out.println(cc1); short ss = (short)cc1; // 变量声明 // 变量类型 变量名; int iage2; // 变量的赋值 // 变量名=值； iage2 = 100; // 变量类型 变量名 = 值; int iage3 = 1000; } // 方法的结束大 }