Java中的輸入是指從數(shù)據(jù)源等讀到Java程序中，這里的數(shù)據(jù)源可以是文件，內(nèi)存或網(wǎng)絡(luò)連接，輸出則是指從Java程序中寫到目的地。
輸入輸出流可以分為以下幾種類型(暫時不考慮File類)
Java IO共涉及40多個類，下圖是字節(jié)流各個類之間的關(guān)系
InputStream
InputStream的子類及其說明有如下所示
OutputStream
OutputStream的子類及其說明有如下所示
對于類中方法的熟悉不詳述了，可以參照J(rèn)DK文檔，或者可以試著在IDE中，實(shí)例化上面的類，使用此類對象時，按下.之后，會出現(xiàn)提示框，再一個一個熟悉就好了。
簡單示例
了解了常用的字節(jié)流類，下面以文件數(shù)據(jù)的輸入輸出說明以上類的使用。
1.在java程序中生成1~20的平方數(shù)，并輸出到文件中。
package com.songpu;import java.io.BufferedOutputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.PrintStream;public class MyFileOutputStream {
public static void main (String[] args) throws IOException{ try{
FileOutputStream fos = new FileOutputStream("F:\\test1.txt");
BufferedOutputStream bos = new BufferedOutputStream(fos,1024);
PrintStream ps = new PrintStream(bos,false);
System.setOut(ps); for(int i= 0;i<20;i++){
System.out.println(i*i);
}
ps.close();
}catch(IOException e){
e.printStackTrace();
}
}
}2.將剛才生成的文件中的數(shù)據(jù)輸入到程序，并將其打印到屏幕
package com.songpu;import java.io.*;public class MyFlieInputStream { public static void main(String[] args) throws IOException {
File file = new File("F:\\test1.txt");
FileInputStream in = new FileInputStream(file);
BufferedInputStream bis = new BufferedInputStream(in); byte[] bytes = new byte[(int) file.length()];
do {
bis.read(bytes);
System.out.println(new String(bytes));
}while (bis.read() != -1);
in.close();
}
}再以序列化與反序列化的例子說明ObjectInputStream和ObjectOutputStream的使用
Java序列化是將對象變成二進(jìn)制形式的一連串字符描述的過程，反序列化就是序列化的相反過程，把這些字符重建為對象。
序列化和反序列化的作用，是保存對象到文件或數(shù)據(jù)庫中，使對象能夠傳輸，序列化的要求是實(shí)現(xiàn)Serializable接口，代碼如下所示
package com.songpu.serial;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;import java.io.OutputStream;import java.io.Serializable;/*
* 待序列化的類，實(shí)現(xiàn)序列化接口
*/class Person implements Serializable{ public String name; public int age; public Person(String name, int age) { super(); this.name = name; this.age = age;
} public String getName() { return name;
} public void setName(String name) { this.name = name;
} public int getAge() { return age;
} public void setAge(int age) { this.age = age;
}
}/*
* 測試類
*/public class SerialTest{ public static void main(String[] args) throws IOException, ClassNotFoundException{
ObjectOutputStream oos = new ObjectOutputStream(new FileOutputStream("F:\\test.txt"));
Person p0 = new Person("tangsong",21);
oos.writeObject(p0);
oos.flush();
oos.close();
deserial();
}
public static void deserial() throws ClassNotFoundException, IOException{
ObjectInputStream ois = new ObjectInputStream(new FileInputStream("F:\\test.txt"));
Person p1 = (Person)ois.readObject();
ois.close();
System.out.println("Name="+p1.getName()+";Age="+p1.getAge());
}
}運(yùn)行上述代碼的結(jié)果如下：
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