ECE 462Object-Oriented Programmingusing C++ and JavaLecture 10Yung-Hsiang [email protected] 6 2Lab 5: Comparing the Performance of C++ and Java Container Classesmeasure the time • C++ and Java (linked) lists of strings– push_back 1 million strings– push_front 1 million strings• C++ and Java set of Student objects– insert 1 million distinct objects– insert 1 million duplicate objectsweek 6 3Container Classes & Methods• Some container classes (such as set) need special methods.• C++ set needs – operator == to determine whether a new element is already in the set– operator < to order the elements in the set• Java Set needs– class to implement Comparable interface– override compareTo methodweek 6 4Self Test(Do Java containers copy objects?)import java.io.*;import java.util.*;// similar to VectorForClassType.ccclass X{private int x_val;public X(int val) { x_val = val; }public int getVal() { return x_val; }public void setVal(int val) { x_val = val; }public String toString(){String rtv = "val = " + x_val;return rtv;}}week 6 5class VectorForClass {public static void main( String[] args ){Vector<X> XVec = new Vector<X>();X x1 = new X(2);X x2 = new X(3);X x3 = new X(5);XVec.addElement(x1);XVec.addElement(x2);XVec.addElement(x3);System.out.println(XVec);x2.setVal(1000);System.out.println(XVec);}}same output?week 6 6Self Test#include <iostream>#include <vector> using namespace std;int callcount = 0;class X { int x_val;public:X(int val = 74) { x_val = val; cout << "X(int) " << x_val << endl; callcount ++; }X (const X & xin) { x_val = xin.x_val; cout << "X(const X&) " << x_val << endl; callcount += 2; }X & operator = (const X & xin){ if ( this != &xin ) { x_val = xin.x_val; }cout << "operator = (const X&) " << x_val << endl; callcount += 3; return *this; }week 6 7int getVal(void) const { return x_val; }friend ostream & operator << (ostream & os, const X & xin); };ostream & operator << (ostream & os, const X & xin) {os << xin.x_val; return os;} int sum(vector<X> v ) {cout << "\nvector sum is: ";int sum = 0;vector<X>::iterator p = v.begin();while ( p != v.end() ){sum += p->getVal();p ++;}cout << sum << endl; return sum;}void print( vector<X> v ) {cout << "\nvector size is: " << v.size() << endl;vector<X>::iterator p = v.begin();while ( p != v.end() ){cout << (*p) << " "; p ++;cout << " ";}cout << endl;sum(v);}?week 6 8int main(){vector<X> vec; X x1( 2 ); X x2( 3 ); X x3( 5 ); vec.push_back( x1 );vec.push_back( x2 );vec.push_back( x3 );vec[2] = x1;print( vec ); cout << "callcount = " << callcount << endl;return 0;}?week 6 9How to Improve the Speed?(avoid copying objects)void print(vector<X> & ); // object reference, chapter 9void print(vector<X> & v ) {cout << "\nvector size is: " << v.size() << endl;vector<X>::iterator p = v.begin();while ( p != v.end() )cout << (*p++).getp() << " "; cout << endl << endl;}week 6 10Java IO Stream• Java has a wide selection of IO streams, for different data types, buffered or not, whether the file is readable from a text editor, and file size.•example: 98– 4-byte integer (hexadecimal): 00 00 00 62–62– ASCII: 39 38• Java IO streams do not provide buffering, unless BufferOutputStream is used.• Java streams can be combined.week 6 11File IO for Classimport java.io.*;class ClassWithFileIO{private int c_iVal;private double c_dVal;private String c_sVal;public ClassWithFileIO(String fileName) throws Exception{DataInputStream dis =new DataInputStream(new FileInputStream(fileName));c_iVal = dis.readInt();c_dVal = dis.readDouble();c_sVal = dis.readUTF();dis.close();System.out.println("c_iVal = " + c_iVal +"\nc_dVal = " + c_dVal +"\nc_sVal = " + c_sVal);}public ClassWithFileIO(int ival, double dval, String sval){c_iVal = ival;c_dVal = dval;c_sVal = sval;}week 6 12public void writeFile(String fileName) throws Exception{DataOutputStream dos =new DataOutputStream(new FileOutputStream(fileName) );dos.writeInt(c_iVal);dos.writeDouble(c_dVal);dos.writeUTF(c_sVal);dos.close();}}class WriteReadClass {public static void main( String[] args ) throws Exception{ClassWithFileIO cfio1 =new ClassWithFileIO(-15, 62.347, "Purdue Boiler");cfio1.writeFile("classdata");ClassWithFileIO cfio2 =new ClassWithFileIO("classdata");}}ECE 462Object-Oriented Programmingusing C++ and JavaLecture 11Yung-Hsiang [email protected] 6 14C++ IO Stream• open file for output: ofstream fileout(“filename”);fileout << 123 << “a string” << endl;ofstream fileout(“filename”, ios::app); // append mode• open file for input:ifstream filein(“filename”);int x;filein >> x;• open file for both input and output:fstream finout(“filename”, ios::in | ios::out);ios::binary for binary fileweek 6 15#include <iostream>#include <fstream>#include <string>using namespace std;class ClassWithFileIO{private:int c_iVal;double c_dVal;string c_sVal;public:ClassWithFileIO(string fileName){ifstream fin(fileName.c_str(), ios::binary);fin >> c_iVal;fin >> c_dVal;fin >> c_sVal;fin.close();cout << "c_iVal = " << c_iVal<< "\nc_dVal = " << c_dVal<< "\nc_sVal = " << c_sVal << endl;}void writeFile(string fileName){ofstream fout(fileName.c_str(), ios::binary);fout << c_iVal;fout << c_dVal;fout << c_sVal;fout.close();}ClassWithFileIO(int ival, double dval, string sval){c_iVal = ival;c_dVal = dval;c_sVal = sval;week 6 16}};int main(int argc, char * argv[]){ClassWithFileIO cfio1(-217, 64.35, "Purdue Boiler");cfio1.writeFile("classdata");ClassWithFileIO cfio2("classdata");return 0;}week 6 17Declaration, Definition, Initialization• declaration: inform the compiler the existence of an identifier (variable name, function name, class name ...)• definition: for variable, memory is allocated; for function, code is written• initialization: assign (default) value to variable• You should always initialize all variables and objects. Uninitialized values are a common source for errors.• Never leave anything uninitialized.week 6 18Declaration and Definitionint xvar; // definitionint xvar = 4; // definition and initializationextern int xvar; // declaration only// defined somewhere elseclass Student; // declarationclass Student { // definitionint s_id;int s_year;};double func(int, float); // declarationdouble func(int