JAVA

1.Basic DataType

int Data=1;
float Data=1.0f;
double Data=1.1;
char Data='A';
boolean Data=true;
byte Data=1;
short Data=1;
long Data=1000000L;

2.Blocks

if(condition){ do ..}
do { ... }while(condition);
for(condition){ do ..}
switch(condition) {
    case condition:
    default:
        break;
}

3.Class

class ClassName{
    var var1;//instance variable
    ClassName(){
        constructor1;
    }
    returnType methodName(var1,var2,var3 ...){
        ...
    }
}
ClassName a=new ClassName();
a.var1=xxx;

//public menber can be accessed in the inside of its defination class and the outside
//Private only be accessed in the defination class inside;

overload method

public class test {
    public static void main(String[] args) {
        hello demo = new hello();
        System.err.println(demo.db(3));
        System.err.println(demo.db(33.3));
    }
}

class hello {
    int db(int a) {
        return a * 2;
    }

    double db(double a) {
        return a * 2;
    }

    long db(long a) {
        return a * 2;
    }
}

overload constractor

class demo{
    int i;
    demo(int i){
        x=i;
    }
    demo(double i){
        x=i;
    }
}

Static

the variables can be changed or affected by any object s

static int a=2;
//the static create and can be accessed by any objects just like a global variables

public class test {
    public static void main(String[] args) {
        // Demo demo=new Demo();
        //the static method is not nessary to new a object;
        //and its not use like object.xxx;and like className.xxx;
        System.err.println(Demo.passobject("hello"));
    }
}

class Demo {
    static String passobject(String oj) {
        return new String(oj);
    }
}

static block

main:
//the static block start run when the object is allocted and can use to init static value
    System.err.println(Demo.name);// alex
class:
    static String name;
    static {
        name = "alex";
    }