Android java 学习笔记 1

目录

• • • 01th_hello
    • 02th_hello
    • 03th_var
    • 04th_function
    • 05th_param
    • 06th_oop
    • 07th_Enc
    • 08th_extends
    • 09th_cnv

01th_hello

hello.c

#include <stdio.h>

int main(int argc, char **argv)
{
	printf("Hello, world!\n");
	return 0;
}

Hello.java

public class Hello {
	public static void main(String args[]) {
		System.out.println("Hello, world!");
	}
}

02th_hello

hello.c

#include <stdio.h>

int main(int argc, char **argv)
{
	int i = 0;

	for (i = 0; i < 3; i++)
		printf("Hello, world!\n");
	return 0;
}

Hello.java

public class Hello {
	public static void main(String args[]) {
		int i = 0;
		for (i = 0; i < 3; i++) {
			System.out.println("Hello, world!");
		}
	}
}

03th_var

var.c

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
	int   a = 3;
	float f = 3.14;

	int* p = malloc(10*sizeof(int));
	char str[100];
	free(p);

	return 0;
}

Var.java

public class Var {
	public static void main(String args[]) {
		int   a = 3;
		float f = (float)3.14;
		float f2 = 3.14f;

		int i = 4;
		short s = 4;
		short s2 = (short)40000;

		//s = i;
		s = (short)(s + 1);  
		s = (short)(s + s2);

		/* Java has no pointer */
		//int* p = malloc(10*sizeof(int));
		int p[] = new int[10];
		int p2[] = {1,2,4}; /* static alloc */
		
		//char str[100];
		char str[] = new char[100];

		//char str2[] = "abc";

		String str2 = "abc";

		p = null;
		p2 = null;
		str = null;
		str2 = null;
	}
}

04th_function

Function.java

public class Function {
	public static void main(String args[]) {
		System.out.println(add(1,2));
		System.out.println(add(1,2, 3));
		System.out.println(add(1.0f, 2.0f));
	}

	public static int add (int x, int y) {
		return x + y;	
	}
	
	public static int add (int x, int y, int z) {
		return x + y + z;	
	}

	public static float add (float x, float y) {
		return x + y;	
	}

}

05th_param

Param.java

public class Param {
	public static void main(String args[]) {
		int x = 1;
		fun (x);

		int p[] = new int[1];
		p[0] = 123;

		System.out.println("Before fun2: "+p[0]);
		fun2(p);
		System.out.println("After fun2: "+p[0]);
		
		System.out.println(x);
	}

	public static void fun(int x) {
		x = 100;
	}		

	public static void fun2(int[] p) {
		p[0] = 200;
	}		

}

06th_oop

person.c

#include <stdio.h>

int main(void)
{
	char *name1 = "zhangsan";
	char *name2 = "lisi";

	printf("guangdogn %s\n", name1);
	printf("guangdogn %s\n", name2);

	return 0;
}

person2.c

#include <stdio.h>

struct person {
	char *name;
};

int main(void)
{
	struct person p1 = {"zhangsan"};
	struct person p2 = {"lisi"};

	printf("%s\n", p1.name);
	printf("%s\n", p2.name);

	return 0;
}

person3.c

#include <stdio.h>

struct person {
	char *name;
	void (*printName)(struct person *per);
};

void printName(struct person *per)
{
	printf("guangdong %s\n", per->name);
}

int main(void)
{
	struct person p1 = {"zhangsan", printName};
	struct person p2 = {"lisi", printName};

	//printf("%s\n", p1.name);
	//printf("%s\n", p2.name);
	p1.printName(&p1);
	p2.printName(&p2);

	return 0;
}

Oop.java

class Person {
	String name;
	String getName() {
		return "guangdong "+name;
	}
};


public class Oop {
	public static void main(String args[]) {
		Person p1 = new Person();
		p1.name = "zhangsan";

		Person p2 = new Person();
		p2.name = "lisi";

		System.out.println(p1.getName());
		System.out.println(p2.getName());
	}
}

Oop2.java

class Person {
	String name;
	String getName() {
		return "guangdong "+name;
	}

	/* construct function */	
	public Person (String n) {
		name = n;
	}
	
};


public class Oop2 {
	public static void main(String args[]) {
		Person p1 = new Person("zhangsan");
		Person p2 = new Person("lisi");

		System.out.println(p1.getName());
		System.out.println(p2.getName());
	}
}

Oop3.java

class Person {
	String name;
	int age;
	String getName() {
		return "guangdong "+name;
	}

	/* construct method */	
	public Person () {
		name = "null";
		age  = 0;
	}

	public Person (String name) {
		this.name = name;
	}

	public Person (String name, int age) {
		this.name = name;
		this.age  = age; 
	}
	
};


public class Oop3 {
	public static void main(String args[]) {
		Person p1 = new Person("zhangsan");
		Person p2 = new Person("lisi");
		Person p3 = new Person();
		Person p4 = new Person("wangwu", 6);

		System.out.println(p1.getName());
		System.out.println(p2.getName());
		System.out.println(p3.getName());
		System.out.println(p4.getName());
	}
}

Oop4.java

class Person {

	static int count;
	
	String name;
	int age;
	String getName() {
		return "guangdong "+name;
	}

	/* construct method */	
	public Person () {
		count++;
		name = "null";
		age  = 0;
	}

	public Person (String name) {
		count++;
		this.name = name;
	}

	public Person (String name, int age) {
		count++;
		this.name = name;
		this.age  = age; 
	}

	static void printPerson () {
		System.out.println("This is a class of Person");
	}
	
};


public class Oop4 {
	public static void main(String args[]) {
		Person p1 = new Person("zhangsan");
		Person p2 = new Person("lisi");
		Person p3 = new Person();
		Person p4 = new Person("wangwu", 6);

		System.out.println(p1.getName());
		System.out.println(p2.getName());
		System.out.println(p3.getName());
		System.out.println(p4.getName());

		Person.printPerson();
		System.out.println(Person.count);
	}
}

Oop5.java

class Person {

	static int count;
	
	String name;
	int age;
	String getName() {
		return "guangdong "+name;
	}

	static {
		System.out.println("static block");		
	}

	{
		System.out.println("construct block");
		count ++;
	}

	/* construct method */	
	public Person () {
		System.out.println("construct method: Person 1");
		name = "null";
		age  = 0;
	}

	public Person (String name) {
		System.out.println("construct method: Person 2");
		this.name = name;
	}

	public Person (String name, int age) {
		System.out.println("construct method: Person 3");
		this.name = name;
		this.age  = age; 
	}

	static void printPerson () {
		System.out.println("This is a class of Person");
	}
	
};


public class Oop5 {
	public static void main(String args[]) {
		Person p1 = new Person("zhangsan");
		Person p2 = new Person("lisi");
		Person p3 = new Person();
		Person p4 = new Person("wangwu", 6);

		System.out.println(p1.getName());
		System.out.println(p2.getName());
		System.out.println(p3.getName());
		System.out.println(p4.getName());

		Person.printPerson();
		System.out.println(Person.count);
	}
}

07th_Enc

class Person {
	private int age;

	public void setAge(int age) {
		if (age < 0 || age > 200)
			age = 0;
		else {
			this.age = age;
		}
	}

	public int getAge() {
		return age;
	}
	
}

public class Enc {
	public static void main(String args[]) {
		Person per = new Person();
		//per.age = -1;
		per.setAge(-1);

		System.out.println(per.getAge());
	}
}

08th_extends

Ext.java

class Person {
	private int age;

	public void setAge(int age) {
		if (age < 0 || age > 200)
			age = 0;
		else {
			this.age = age;
		}
	}

	public int getAge() {
		return age;
	}	
}

class Student extends Person{
}

public class Ext {
	public static void main (String args[]) {
		Student stu = new Student();

		stu.setAge(10);

		System.out.println(stu.getAge());
	}
}

Ext2.java

class Person {
	private int age;

	public void setAge(int age) {
		if (age < 0 || age > 200)
			age = 0;
		else {
			this.age = age;
		}
	}

	public int getAge() {
		return age;
	}	
}

class Student extends Person{
	private String school;

	public void setSchool(String school) {
		this.school = school;
	}

	public String getSchool() {
		return school;
	}	

	public Student(String school) {
		this.school = school;
	}
	
}

public class Ext2 {
	public static void main (String args[]) {
		Student stu = new Student("ustc");

		stu.setAge(10);

		System.out.println(stu.getAge());
		System.out.println(stu.getSchool());
	}
}

Ext3.java

class Person {
	private int age;

	public void setAge(int age) {
		if (age < 0 || age > 200)
			age = 0;
		else {
			this.age = age;
		}
	}

	public int getAge() {
		return age;
	}	

	public void printInfo() {
		System.out.println("age = "+age);
	}
}

class Student extends Person{
	private String school;

	public void setSchool(String school) {
		this.school = school;
	}

	public String getSchool() {
		return school;
	}	

	public Student(String school) {
		this.school = school;
	}

	/* override */
	public void printInfo() {
		System.out.println("school = "+school+"; age = "+getAge());
	}
	
}

public class Ext3 {
	public static void main (String args[]) {
		Student stu = new Student("ustc");

		stu.setAge(10);

		System.out.println(stu.getAge());
		System.out.println(stu.getSchool());
		stu.printInfo();
	}
}

Ext4.java

class Person {
	private int age;

	public void setAge(int age) {
		if (age < 0 || age > 200)
			age = 0;
		else {
			this.age = age;
		}
	}

	public int getAge() {
		return age;
	}	

	public void printInfo() {
		System.out.println("age = "+age);
	}

	public Person () {System.out.println("Person ()");}
	public Person (int age) {
		System.out.println("Person (int age)");
		this.age = age;
	}
	
}

class Student extends Person{
	private String school;

	public void setSchool(String school) {
		this.school = school;
	}

	public String getSchool() {
		return school;
	}	

	public Student(String school) {
		/* will call the super() */
		//super();
		super(5);
		System.out.println("Student(String school)");
		this.school = school;
	}

	/* override */
	public void printInfo() {
		System.out.println("school = "+school+"; age = "+getAge());
	}
	
}

public class Ext4 {
	public static void main (String args[]) {
		Student stu = new Student("ustc");

		//stu.setAge(10);

		System.out.println(stu.getAge());
		System.out.println(stu.getSchool());
		stu.printInfo();
	}
}

Ext5.java

class Father {
	private int money;	

	public int getMoney() {return money; }
	public void setMoney(int money) {this.money = money; }

	public void printInfo() {System.out.println("This is Father");}

	private void printInfo2() {System.out.println("This is Father");}
}

class Son extends Father{
	public void printInfo() {System.out.println("This is son");}

	public void printInfo2() {System.out.println("This is Father");}
	
}

public class Ext5 {
	public static void main (String args[]) {
		Son son = new Son();
		son.setMoney(100);
		//son.printInfo();
	}
}

Ext6.java

abstract class Father {
	private int money;	

	public int getMoney() {return money; }
	public void setMoney(int money) {this.money = money; }

	public abstract void study();
}

class Son extends Father{
	public void study() {System.out.println("I am study"); }
	
}

public class Ext6 {
	public static void main (String args[]) {
		//Father f = new Father();
		Son son = new Son();
		son.study();

	}
}

Ext7.java

abstract class Father {
	private int money;	

	public int getMoney() {return money; }
	public void setMoney(int money) {this.money = money; }

	public abstract void study();
}

interface A {
	public static final int i = 10;
	public abstract int getNum();
}

interface B {
	public static String name = "InterfaceB";
	public abstract String getName();
}

class Son extends Father implements A,B{
	public int getNum() {return i;}
	public String getName() {return name;}
	public void study() {System.out.println("I am study"); }
	
}

public class Ext7 {
	public static void main (String args[]) {
		Son son = new Son();
		System.out.println(son.getName());
		son.study();
	}
}

09th_cnv

Cnv.java

class Father {
	private int money;	

	public int getMoney() {return money; }
	public void setMoney(int money) {this.money = money; }

	public void printInfo() {System.out.println("This is Father");}

}

class Son extends Father{
	public void printInfo() {System.out.println("This is son");}
	public void playGame() {System.out.println("playGame ...");}
	
}

class Daughter extends Father{
	public void printInfo() {System.out.println("This is daughter");}

	
}

public class Cnv {
	public static void main (String args[]) {
		Son son = new Son();
		Daughter daughter = new Daughter();

		Father f = son; /*  */
		f.printInfo();

		//f.playGame();

		f = daughter;
		f.printInfo();
		
	}
}

Cnv2.java

class Father {
	private int money;	

	public int getMoney() {return money; }
	public void setMoney(int money) {this.money = money; }

	public void printInfo() {System.out.println("This is Father");}

}

class Son extends Father{
	public void printInfo() {System.out.println("This is son");}
	public void playGame() {System.out.println("playGame ...");}
	
}

class Daughter extends Father{
	public void printInfo() {System.out.println("This is daughter");}

	
}

public class Cnv2 {
	public static void main (String args[]) {
		Father f = new Son();
		Son son = (Son)f;   /* Son son = new Son(); */
	}
}

Cnv3.java

class Father {
	private int money;	

	public int getMoney() {return money; }
	public void setMoney(int money) {this.money = money; }

	public void printInfo() {System.out.println("This is Father");}

}

class Son extends Father{
	public void printInfo() {System.out.println("This is son");}
	public void playGame() {System.out.println("playGame ...");}
	
}

class Daughter extends Father{
	public void printInfo() {System.out.println("This is daughter");}

	
}

public class Cnv3 {
	public static void main (String args[]) {
		Father f = new Father();
		Son s = new Son();
		Daughter d = new Daughter();

		print(f);
		print(s);
		print(d);
	}

	public static void print(Father f) {
		f.printInfo();
	}

	public static void print(Son s) {
		s.printInfo();
	}

	public static void print(Daughter d) {
		d.printInfo();
	}
	
}

Cnv4.java

class Father {
	private int money;	

	public int getMoney() {return money; }
	public void setMoney(int money) {this.money = money; }

	public void printInfo() {System.out.println("This is Father");}

}

class Son extends Father{
	public void printInfo() {System.out.println("This is son");}
	public void playGame() {System.out.println("playGame ...");}
	
}

class Daughter extends Father{
	public void printInfo() {System.out.println("This is daughter");}

	
}

public class Cnv4 {
	public static void main (String args[]) {
		Father f = new Father();
		Son s = new Son();
		Daughter d = new Daughter();

		print(f);
		print(s);
		print(d);
	}

	public static void print(Father f) {
		f.printInfo();
	}

	
}

Cnv5.java

class Father {
	private int money;	

	public int getMoney() {return money; }
	public void setMoney(int money) {this.money = money; }

	public void printInfo() {System.out.println("This is Father");}
	public void drink() {System.out.println("drink ...");}

}

class Son extends Father{
	public void printInfo() {System.out.println("This is son");}
	public void playGame() {System.out.println("playGame ...");}
	
}

class Daughter extends Father{
	public void printInfo() {System.out.println("This is daughter");}
	public void dance() {System.out.println("dance ...");}

	
}

public class Cnv5 {
	public static void main (String args[]) {
		Father f = new Father();
		Son s = new Son();
		Daughter d = new Daughter();

		printAction(f);
		printAction(s);
		printAction(d);
	}

	public static void printAction(Father f) {
		if (f instanceof Son) {
			Son son = (Son)f;
			son.playGame();
		}
		else if (f instanceof Daughter) {
			Daughter d = (Daughter)f;
			d.dance();
		}
		else if (f instanceof Father) {
			f.drink();
		}
	
		
	}

	
}