标签：style blog class code java tar
关键字：
被Java语句赋予特殊含义的单词，所有关键字都是小写
标识符：
程序中自定义的一些名称，由字母、数字、_ 以及 $ 符号组成，数字不能开头，区分大小写（命名规范）
注释：
// 单行注释 /* 多行注释 */ /** 文档注释 */
常量：
整数常量、小数常量、布尔型常量、字符常量、字符串常量、null
变量：
数据类型 变量名 [= 初始化值];
数据类型：
基本数据类型、引用数据类型
数据类型转换：
package g.javase; public class VarDemo { public static void main(String[] args) { // 数据类型 变量名 [= 初始化值]; int x = 4; System.out.println("x = " + x); byte b = 3; b = (byte) (b + 1); // 强制转换 System.out.println("b = " + b); char ch = 97; System.out.println("ch = " + ch); char ch2 = ‘a‘; System.out.println("ch2 = " + (ch2 + 1)); } }
运算符：
package g.javase; public class OperateDemo { public static void main(String[] args) { int x = 1234; System.out.println(x / 1000); System.out.println("5 + 5 = " + 5 + 5); // 字符串连接符 System.out.println(3 % 5); System.out.println(-3 % 5); System.out.println(3 % -5); System.out.println(2 * 8); System.out.println(2 << 3); int a = 5; int b = 6; System.out.println("a = " + a + "\tb = " + b); a = a ^ b; b = a ^ b; a = a ^ b; System.out.println("a = " + a + "\tb = " + b); } }
流程控制：
函数：
修饰符 返回值类型 函数名(参数列表) { 执行语句; [return 返回值;] }
函数的重载：在同一个类中，允许存在一个以上的同名函数，只要它们的参数个数或参数类型不同即可
数组：
同一类型数据的集合
元素类型[] 数组名 = new 元素类型[数组长度];
package g.javase; import java.util.Arrays; public class ArrayDemo { public static void main(String[] args) { int[] a1 = new int[3]; a1[0] = 1; a1[1] = 2; a1[2] = 3; int[] a2 = new int[] { 1, 2, 3 }; int[] a3 = { 1, 2, 3 }; System.out.println("a1: " + Arrays.toString(a1)); System.out.println("a2: " + Arrays.toString(a2)); System.out.println("a3: " + Arrays.toString(a3)); } }
补充：
package g.javase; public class BinarySearch { public static void main(String[] args) { } public static int binarysearch(int[] a, int k) { int max = a.length - 1; int min = 0; int mid; while (min <= max) { mid = (min + max) / 2; if (k > a[mid]) { min = mid + 1; } else if (k < a[mid]) { max = mid - 1; } else { return mid; } } return -1; } }
package g.javase; public class Hex { public static void main(String[] args) { int num = 28; System.out.println(trans(num, 1, 1)); // to Binary System.out.println(trans(num, 7, 3)); // to Oct System.out.println(trans(num, 15, 4)); // to Hex System.out.println(Integer.toBinaryString(num)); System.out.println(Integer.toOctalString(num)); System.out.println(Integer.toHexString(num)); } public static String trans(int num, int base, int offset) { char[] chs = { ‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘, ‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘, ‘F‘ }; char[] arr = new char[32]; int index = arr.length; while (num != 0) { int temp = num & base; arr[--index] = chs[temp]; num = num >>> offset; } return toString(arr, index); } public static String toString(char[] arr, int index) { String temp = ""; for (int x = index; x < arr.length; x++) { temp = temp + arr[x]; } return temp; } }
package g.javase; import java.util.Arrays; public class SortDemo { public static void main(String[] args) { int[] a = { 12, 9, 23, 77, 6, 34}; int[] b = { 12, 9, 23, 77, 6, 34}; System.out.println(Arrays.toString(a)); select(a); System.out.println(Arrays.toString(a)); System.out.println(Arrays.toString(b)); select(b); System.out.println(Arrays.toString(b)); } // 选择排序 public static void select(int[] a) { for (int i = 0; i < a.length - 1; i++) { for (int j = i + 1; j < a.length; j++) { if (a[i] > a[j]) { int t = a[i]; a[i] = a[j]; a[j] = t; } } } } // 冒泡排序 public static void bubble(int[] a) { for (int i = 0; i < a.length - 1; i++) { for (int j = 0; j < a.length - 1 - i; j++) { if (a[j] > a[j + 1]) { int t = a[j]; a[j] = a[j + 1]; a[j + 1] = t; } } } } }
Java SE(1)：基础语法,布布扣,bubuko.com
标签：style blog class code java tar
原文地址：http://www.cnblogs.com/geb515/p/3710528.html
