Stirng：
构造器：
1：String str = "abc";
2: String str = new String("abc");
3：String str = new String(byte[],start,length);
方法：
1：charAt(index) 2：length() ?3:subString(start);
4: subString(start,end) ?5:valueOf(XXX)
6: getBytes()
StringBuffer、StringBuilder
1:append(); 2:toString(); new StringBuilder();
包装类
Integer: 自动装箱、自动拆箱
Integer in = 10; // valueOf(int)
int num = in;// intValue();
Date
new Date();
new Date(1L)
SimpleDateFormate
new SimpleDateFormate("yyyy-MM-dd").format(date);
异常
出现异常的解决方案：
try-catch:
try{
//代码
}catch(Exception e){
//处理方式
e.printStackTrance();
}finally{
// 关闭
}
throws:
function() throws Excepiton{
}
throw：
声明了一个异常对象
function (){
new Exception();
}
IO流：代码步骤
//1:创建流
Input/Output Stream ?--> 万能
Reader/Writer --> 读取文件 字符
= new FileInputStream(读取的文件);
= new FileOutputStream(写出的文件);
= BufferedReader(new InputStreamReader(new InputStream(读取的文件)));
= BufferedWriter(new OutputStreamWriter(new OutputStream(写出的文件)));
//2：读取/写出
XXX.read(byte[]);
while((len = XXX.read(byte[]))!=-1){
StringBuilder.append(new String(byte[],0,len))
}
XXX.write(字符串.getBytes());
//3：操作
//4：关闭
Socket：代码步骤
TCP:客户端和服务器端
client:
//1:创建对象 ?建立链接
Socket client = new Socket(ip,port);
//2:获取流
OutputStream os = client.getOutputStream();
//3:发送数据
os.write();
//4：关闭
os.close();
client.close();
server:
//1:创建对象
ServerSocket server = new ServerSocket(port);
//2:获取客户端对象
Socket client = server.accept();
//3:获取流
????InputStream is = client.getInputStream();
//4:操作
is.read();
//5:关闭
is.close();
client.close();
server.close();
UDP:发送端和接收端
send:
//1:创建对象
DatagramSocket send = new DatagramSocket(port);
//2:发送数据包
//2-1 创建数据包对象
DatagramPacket packet = new DatagramPacket(
ip,port,byte[],length);
send.send(packet);
//3:关闭
rec:
//1:创建对象
DatagramSocket rec = new DatagramSocket(port);
//2：接受数据包
//2-1 创建接受包
DatagramPacket packet = new DatagramPacket(
byte[],length);
rec.recive(packet);