Hello, World.
public class learn { public static void main(String[] args){ System.out.println("hi"); } }
Built-in data types:
int, double, boolean, char, String
类型转换：
字符串转为数字：
String s1 = "1234"; String s2 = "1234.123"; int a = Integer.parseInt(s1); double b = Double.parseDouble(s2); long c = Long.parseLong(s1); System.out.println(a); //1234 System.out.println(b); //1234.123 System.out.println(c); //1234
数字转换成字符串：
double d = 123.4; String s = String.valueOf(d); System.out.println(s); //123.4
字符串加数字， 生成字符串
"1234"+99 --> "123499"
Switch：
switch(day){ case 0: System.out.println("Sun"); break; case 1: System.out.println("Mon"); break; }
数组：
double[] b = new double[N];
Input:
Scanner in=new Scanner(System.in); String readLine = in.nextLine(); System.out.println(readLine);
字符串长度：
s.length()
原文：http://www.cnblogs.com/XingyingLiu/p/5152771.html