BINARY I/O - Introduction to Java Programming: Comprehensive Version - page 693

for objects in addition to primitive-type values and strings. Since ObjectInputStream /
ObjectOutputStream contains all the functions of DataInputStream /
DataOutputStream , you can replace DataInputStream / DataOutputStream completely
with ObjectInputStream / ObjectOutputStream .
ObjectInputStream extends InputStream and implements ObjectInput and
ObjectStreamConstants , as shown in Figure 17.16. ObjectInput is a subinterface of
DataInput ( DataInput is shown in Figure 17.9). ObjectStreamConstants contains the
constants to support ObjectInputStream / ObjectOutputStream .

VideoNote

Object I/O

«interface»
ObjectStreamConstants

java.io.InputStream

«interface»
java.io.DataInput

«interface»
java.io.ObjectInput

java.io.ObjectInputStream

+ObjectInputStream(in: InputStream) +readObject(): Object Reads an object.

F IGURE 17.16

ObjectInputStream can read objects, primitive-type values, and strings.

ObjectOutputStream extends OutputStream and implements ObjectOutput and
ObjectStreamConstants , as shown in Figure 17.17. ObjectOutput is a subinterface of
DataOutput ( DataOutput is shown in Figure 17.10).

«interface»
ObjectStreamConstants

java.io.OutputStream

«interface»
java.io.DataOutput

«interface»
java.io.ObjectOutput

java.io.ObjectOutputStream

+ObjectOutputStream(out: OutputStream) +writeObject(o: Object): void

Writes an object.

F IGURE 17.17

ObjectOutputStream can write objects, primitive-type values, and strings.

You can wrap an ObjectInputStream / ObjectOutputStream on any InputStream /
OutputStream using the following constructors:

// Create an ObjectInputStream
public ObjectInputStream(InputStream in)

// Create an ObjectOutputStream
public ObjectOutputStream(OutputStream out)

Listing 17.5 writes student names, scores, and the current date to a file named object.dat .

L ISTING 17.5

TestObjectOutputStream.java
1 import java.io.*;
2
3 public class TestObjectOutputStream {