【汇智学堂】JAVA基础（1）

java 基础学习很简单，一本好书，三遍。
第一遍，大概看一遍；
第二遍，仔细看一遍记笔记；
第三遍，从前到后完整敲一遍，从“hello，world”开始。

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

import java.awt.*;
import java.applet.*;

public class APPlet extends Applet{
    public void paint(Graphics g){
        g.drawString("千山鸟飞绝，万径人踪灭。孤舟蓑笠翁，独钓寒江雪。",20,20);
    }
}

public class sample {
    public static void main(String[]args){
        char ch1,ch2;
        ch1=65;
        ch2='B';
        System.out.println("ch1 and ch2:"+ch1+""+ch2);
    }
}

public class sample2 {
    public static void main (String[]args){
        char ch1;
        ch1='A';
        ch1++;
        System.out.println("ch1 is:"+ch1);

    }
}

public class sample3 {
    public static void main (String[]args){
        int x,y;
        float z=3.14f;
        double w=3.1415;
        char c;
        String str;
        String str1="bye";
        c='A';
        str="Hello!Welcome!";
        x=6;
        y=1000;
        System.out.println("int x="+x);
        System.out.println("int y="+y);
        System.out.println("float z="+z);
        System.out.println("double w="+w);
        System.out.println("char c="+c);
        System.out.println("String str="+str);
    }
}

public class sample4 {
    public static void main(String args[]){
        byte b;
        int i=257;
        double d=123.456;
        System.out.println("Casting of int to byte.");
        b=(byte) i;
        System.out.println("b is:"+b);
        System.out.println("Casting of double to int.");
        i=(int)d;
        System.out.println("i is:"+i);
    }
}

public class sample5 {
    public void implictCasting(){
        byte a=0x60;
        int ia=a;
        char b='a';
        int c=b;
        long d=c;
        long e=1000000000L;
        float f=e;
        double g=f;
        String s="hello";
        Object o=s;
    }
    public void explicitCasting(){
        long l=1000000L;
        int i=(int)l;
        double d=12345.678;
        float f=(float)d;
        Object o=new String("Hello");
        String str=(String)o;
    }
}

标签：JAVA,String,int,System,汇智,学堂,println,public,out
来源： https://blog.csdn.net/weixin_44711285/article/details/97164086