用法 int x1 = 2_014; // Underscore in deciaml format int x2 = 2___014; // Multiple consecutive underscores int x3 = 02_014; // Underscore in octal literal int x4 = 0b0111_1011_0001; // Underscore in binary literal int x5 = 0x7_B_1; // Underscores in he