Java program:

//MathOperation.java import java.util.Scanner; public class MathOperation { //A int intNum1; int intNum2; float fNum1; float fNum2; int op; //B public MathOperation() { intNum1 = 0; intNum2 = 0; fNum1 = 0; fNum2 = 0; op = 0; } //C public MathOperation(int n1, int n2, int n) { intNum1 = n1; intNum2 = n2; fNum1 = 0; fNum2 = 0; op = n; } //D public MathOperation(float d1, float d2, int n) { fNum1 = d1; fNum2 = d2; intNum1 = 0; intNum2 = 0; op = n; } //E public String toString() { String str = "CALCULATOR OF LIEM LE"; String str2 = "", str3 = ""; int iRet= 0; float fRet = 0.0f; switch (op) { case 1: // add 2 int str2 = "ADD TWWO INTEGERS"; iRet = intNum1 + intNum2; str3 = intNum1 + " + " + intNum2 + " = " + iRet; break; case 2: // minus 2 int str2 = "MINUS TWWO INTEGERS"; iRet = intNum1 - intNum2; str3 = intNum1 + " - " + intNum2 + " = " + iRet; break; case 3: // multiply 2 int str2 = "MULTIPLY TWWO INTEGERS"; iRet = intNum1 * intNum2; str3 = intNum1 + " * " + intNum2 + " = " + iRet; break; case 4: // divide 2 int str2 = "DIVIDE TWWO INTEGERS"; iRet = intNum1 /intNum2; str3 = intNum1 + " / " + intNum2 + " = " + iRet; break; case 5: // add 2 float str2 = "ADD TWWO DECIMAL NUMBERS"; fRet = fNum1 + fNum2; str3 = fNum1 + " + " + fNum2 + " = " + fRet; break; case 6: // minus 2 floaf str2 = "MINUS TWWO DECIMAL NUMBERS"; fRet = fNum1 - fNum2; str3 = fNum1 + " - " + fNum2 + " = " + fRet; break; case 7: // multiply float str2 = "MULTIPLY TWWO DECIMAL NUMBERS"; fRet = fNum1 * fNum2; str3 = fNum1 + " * " + fNum2 + " = " + fRet; break; case 8: // divide float str2 = "DIVIDE TWWO DECIMAL NUMBERS"; fRet = fNum1 / fNum2; str3 = fNum1 + " / " + fNum2 + " = " + fRet; break; } return str + "\n" + str2 + "\n" + str3 + "\n"; } }