| JavaProgram StructureC# |
package hello;
public class HelloWorld {
public static void main(String[] args) {
String name = "Java";
// See if an argument was passed from the command line
if (args.length == 1)
name = args[0];
System.out.println("Hello, " + name + "!");
}
}登录后复制
| using System;
namespace Hello {
public class HelloWorld {
public static void Main(string[] args) {
string name = "C#";
// See if an argument was passed from the command line
if (args.Length == 1)
name = args[0];
Console.WriteLine("Hello, " + name + "!");
}
}
}登录后复制
|
| JavaCommentsC# |
// Single line
/* Multiple
line */
/** Javadoc documentation comments */登录后复制
| // Single line
/* Multiple
line */
/// XML comments on a single line
/** XML comments on multiple lines */登录后复制
|
| JavaData TypesC# |
Primitive Types
boolean
byte
char
short, int, long
float, double
Reference Types
Object (superclass of all other classes)
String
arrays, classes, interfaces
Conversions
// int to String
int x = 123;
String y = Integer.toString(x); // y is "123"
// String to int
y = "456";
x = Integer.parseInt(y); // x is 456
// double to int
double z = 3.5;
x = (int) z; // x is 3 (truncates decimal) 登录后复制
|
Value Types
bool
byte, sbyte
char
short, ushort, int, uint, long, ulong
float, double, decimal
structures, enumerations
Reference Types
object (superclass of all other classes)
string
arrays, classes, interfaces, delegates
Convertions
// int to string
int x = 123;
String y = x.ToString(); // y is "123"
// string to int
y = "456";
x = int.Parse(y); // or x = Convert.ToInt32(y);
// double to int
double z = 3.5;
x = (int) z; // x is 3 (truncates decimal) 登录后复制
|
| JavaConstantsC# |
// May be initialized in a constructor
final double PI = 3.14; 登录后复制
| const double PI = 3.14;
// Can be set to a const or a variable. May be initialized in a constructor.
readonly int MAX_HEIGHT = 9; 登录后复制
|
| JavaEnumerationsC# |
enum Action {Start, Stop, Rewind, Forward};
// Special type of class
enum Status {
Flunk(50), Pass(70), Excel(90);
private final int value;
Status(int value) { this.value = value; }
public int value() { return value; }
};
Action a = Action.Stop;
if (a != Action.Start)
System.out.println(a); // Prints "Stop"
Status s = Status.Pass;
System.out.println(s.value()); // Prints "70"登录后复制
|
enum Action {Start, Stop, Rewind, Forward};
enum Status {Flunk = 50, Pass = 70, Excel = 90};
No equivalent.
Action a = Action.Stop;
if (a != Action.Start)
Console.WriteLine(a); // Prints "Stop"
Status s = Status.Pass;
Console.WriteLine((int) s); // Prints "70"登录后复制
|
| JavaOperatorsC# |
Comparison
== < > <= >= !=
Arithmetic
+ - * /
% (mod)
/ (integer pision if both operands are ints)
Math.Pow(x, y)
Assignment
= += -= *= /= %= &= |= ^= <<= >>= >>>= ++ --
Bitwise
& | ^ ~ << >> >>>
Logical
&& || & | ^ !
Note: && and || perform short-circuit logical evaluations
String Concatenation
+ 登录后复制
|
Comparison
== < > <= >= !=
Arithmetic
+ - * /
% (mod)
/ (integer pision if both operands are ints)
Math.Pow(x, y)
Assignment
= += -= *= /= %= &= |= ^= <<= >>= ++ --
Bitwise
& | ^ ~ << >>
Logical
&& || & | ^ !
Note: && and || perform short-circuit logical evaluations
String Concatenation
+ 登录后复制
|
| JavaChoicesC# |
greeting = age < 20 ? "What's up?" : "Hello";
if (x < y)
System.out.println("greater");
if (x != 100) {
x *= 5;
y *= 2;
}
else
z *= 6;
int selection = 2;
switch (selection) { // Must be byte, short, int, char, or enum
case 1: x++; // Falls through to next case if no break
case 2: y++; break;
case 3: z++; break;
default: other++;
}登录后复制
|
greeting = age < 20 ? "What's up?" : "Hello";
if (x < y)
Console.WriteLine("greater");
if (x != 100) {
x *= 5;
y *= 2;
}
else
z *= 6;
string color = "red";
switch (color) { // Can be any predefined type
case "red": r++; break; // break is mandatory; no fall-through
case "blue": b++; break;
case "green": g++; break;
default: other++; break; // break necessary on default
}登录后复制
|
| JavaLoopsC# |
while (i < 10)
i++;
for (i = 2; i <= 10; i += 2)
System.out.println(i);
do
i++;
while (i < 10);
for (int i : numArray) // foreach construct
sum += i;
// for loop can be used to iterate through any Collection
import java.util.ArrayList;
ArrayList<Object> list = new ArrayList<Object>();
list.add(10); // boxing converts to instance of Integer
list.add("Bisons");
list.add(2.3); // boxing converts to instance of Double
for (Object o : list)
System.out.println(o);登录后复制
|
while (i < 10)
i++;
for (i = 2; i <= 10; i += 2)
Console.WriteLine(i);
do
i++;
while (i < 10);
foreach (int i in numArray)
sum += i;
// foreach can be used to iterate through any collection
using System.Collections;
ArrayList list = new ArrayList();
list.Add(10);
list.Add("Bisons");
list.Add(2.3);
foreach (Object o in list)
Console.WriteLine(o);登录后复制
|
| JavaArraysC# |
int nums[] = {1, 2, 3}; or int[] nums = {1, 2, 3};
for (int i = 0; i < nums.length; i++)
System.out.println(nums[i]);
String names[] = new String[5];
names[0] = "David";
float twoD[][] = new float[rows][cols];
twoD[2][0] = 4.5;
int[][] jagged = new int[5][];
jagged[0] = new int[5];
jagged[1] = new int[2];
jagged[2] = new int[3];
jagged[0][4] = 5;登录后复制
| int[] nums = {1, 2, 3};
for (int i = 0; i < nums.Length; i++)
Console.WriteLine(nums[i]);
string[] names = new string[5];
names[0] = "David";
float[,] twoD = new float[rows, cols];
twoD[2,0] = 4.5f;
int[][] jagged = new int[3][] {
new int[5], new int[2], new int[3] };
jagged[0][4] = 5;登录后复制
|
| JavaFunctionsC# |
| // Return single value
int Add(int x, int y) {
return x + y;
}
int sum = Add(2, 3);// Return no value
void PrintSum(int x, int y) {
System.out.println(x + y);
}
PrintSum(2, 3);
// Primitive types and references are always passed by value
void TestFunc(int x, Point p) {
x++;
p.x++; // Modifying property of the object
p = null; // Remove local reference to object
}
class Point {
public int x, y;
}
Point p = new Point();
p.x = 2;
int a = 1;
TestFunc(a, p);
System.out.println(a + " " + p.x + " " + (p == null) ); // 1 3 false
// Accept variable number of arguments
int Sum(int ... nums) {
int sum = 0;
for (int i : nums)
sum += i;
return sum;
}
int total = Sum(4, 3, 2, 1); // returns 10登录后复制
| // Return single value
int Add(int x, int y) {
return x + y;
}
int sum = Add(2, 3);// Return no value
void PrintSum(int x, int y) {
Console.WriteLine(x + y);
}
PrintSum(2, 3);
// Pass by value (default), in/out-reference (ref), and out-reference (out)
void TestFunc(int x, ref int y, out int z, Point p1, ref Point p2) {
x++; y++; z = 5;
p1.x++; // Modifying property of the object
p1 = null; // Remove local reference to object
p2 = null; // Free the object
}
class Point {
public int x, y;
}
Point p1 = new Point();
Point p2 = new Point();
p1.x = 2;
int a = 1, b = 1, c; // Output param doesn't need initializing
TestFunc(a, ref b, out c, p1, refp2);
Console.WriteLine("{0} {1} {2} {3} {4}",
a, b, c, p1.x, p2 == null); // 1 2 5 3 True
// Accept variable number of arguments
int Sum(params int[] nums) {
int sum = 0;
foreach (int i in nums)
sum += i;
return sum;
}
int total = Sum(4, 3, 2, 1); // returns 10登录后复制
|
| JavaStringsC# |
// String concatenation
String school = "Harding ";
school = school + "University"; // school is "Harding University"
// String comparison
String mascot = "Bisons";
if (mascot == "Bisons") // Not the correct way to do string comparisons
if (mascot.equals("Bisons")) // true
if (mascot.equalsIgnoreCase("BISONS")) // true
if (mascot.compareTo("Bisons") == 0) // true
System.out.println(mascot.substring(2, 5)); // Prints "son"
// My birthday: Oct 12, 1973
java.util.Calendar c = new java.util.GregorianCalendar(1973, 10, 12);
String s = String.format("My birthday: %1$tb %1$te, %1$tY", c);
// Mutable string
StringBuffer buffer = new StringBuffer("two ");
buffer.append("three ");
buffer.insert(0, "one ");
buffer.replace(4, 7, "TWO");
System.out.println(buffer); // Prints "one TWO three"登录后复制
|
// String concatenation
string school = "Harding ";
school = school + "University"; // school is "Harding University"
// String comparison
string mascot = "Bisons";
if (mascot == "Bisons") // true
if (mascot.Equals("Bisons")) // true
if (mascot.ToUpper().Equals("BISONS")) // true
if (mascot.CompareTo("Bisons") == 0) // true
Console.WriteLine(mascot.Substring(2, 3)); // Prints "son"
// My birthday: Oct 12, 1973
DateTime dt = new DateTime(1973, 10, 12);
string s = "My birthday: " + dt.ToString("MMM dd, yyyy");
// Mutable string
System.Text.StringBuilder buffer = new System.Text.StringBuilder("two ");
buffer.Append("three ");
buffer.Insert(0, "one ");
buffer.Replace("two", "TWO");
Console.WriteLine(buffer); // Prints "one TWO three"登录后复制
|
| JavaException HandlingC# |
// Must be in a method that is declared to throw this exception
Exception ex = new Exception("Something is really wrong.");
throw ex;
try {
y = 0;
x = 10 / y;
} catch (Exception ex) {
System.out.println(ex.getMessage());
} finally {
// Code that always gets executed
}登录后复制
|
Exception up = new Exception("Something is really wrong.");
throw up; // ha ha
try {
y = 0;
x = 10 / y;
} catch (Exception ex) { // Variable "ex" is optional
Console.WriteLine(ex.Message);
} finally {
// Code that always gets executed
}登录后复制
|
| JavaNamespacesC# |
package harding.compsci.graphics;
// Import single class
import harding.compsci.graphics.Rectangle;
// Import all classes
import harding.compsci.graphics.*; 登录后复制
|
namespace Harding.Compsci.Graphics {
...
}
or
namespace Harding {
namespace Compsci {
namespace Graphics {
...
}
}
}
// Import single class
using Rectangle = Harding.CompSci.Graphics.Rectangle;
// Import all class
using Harding.Compsci.Graphics;登录后复制
|
| JavaClasses / InterfacesC# |
Accessibility keywords
public
private
protected
static
// Inheritance
class FootballGame extends Competition {
...
}
// Interface definition
interface IAlarmClock {
...
}
// Extending an interface
interface IAlarmClock extends IClock {
...
}
// Interface implementation
class WristWatch implements IAlarmClock, ITimer {
...
}登录后复制
|
Accessibility keywords
public
private
internal
protected
protected internal
static
// Inheritance
class FootballGame : Competition {
...
}
// Interface definition
interface IAlarmClock {
...
}
// Extending an interface
interface IAlarmClock : IClock {
...
}
// Interface implementation
class WristWatch : IAlarmClock, ITimer {
...
}登录后复制
|
| JavaConstructors / DestructorsC# |
class SuperHero {
private int mPowerLevel;
public SuperHero() {
mPowerLevel = 0;
}
public SuperHero(int powerLevel) {
this.mPowerLevel= powerLevel;
}
// No destructors, just override the finalize method
protected void finalize() throws Throwable {
super.finalize(); // Always call parent's finalizer
}
}登录后复制
|
class SuperHero {
private int mPowerLevel;
public SuperHero() {
mPowerLevel = 0;
}
public SuperHero(int powerLevel) {
this.mPowerLevel= powerLevel;
}
~SuperHero() {
// Destructor code to free unmanaged resources.
// Implicitly creates a Finalize method.
}
}登录后复制
|
| JavaObjectsC# |
SuperHero hero = new SuperHero();
hero.setName("SpamMan");
hero.setPowerLevel(3);
hero.Defend("Laura Jones");
SuperHero.Rest(); // Calling static method
SuperHero hero2 = hero; // Both refer to same object
hero2.setName("WormWoman");
System.out.println(hero.getName()); // Prints WormWoman
hero = null; // Free the object
if (hero == null)
hero = new SuperHero();
Object obj = new SuperHero();
System.out.println("object's type: " + obj.getClass().toString());
if (obj instanceof SuperHero)
System.out.println("Is a SuperHero object.");登录后复制
|
SuperHero hero = new SuperHero();
hero.Name = "SpamMan";
hero.PowerLevel = 3;
hero.Defend("Laura Jones");
SuperHero.Rest(); // Calling static method
SuperHero hero2 = hero; // Both refer to same object
hero2.Name = "WormWoman";
Console.WriteLine(hero.Name); // Prints WormWoman
hero = null ; // Free the object
if (hero == null)
hero = new SuperHero();
Object obj = new SuperHero();
Console.WriteLine("object's type: " + obj.GetType().ToString());
if (obj is SuperHero)
Console.WriteLine("Is a SuperHero object.");登录后复制
|
| JavaPropertiesC# |
private int mSize;
public int getSize() { return mSize; }
public void setSize(int value) {
if (value < 0)
mSize = 0;
else
mSize = value;
}
int s = shoe.getSize();
shoe.setSize(s+1);登录后复制
|
private int mSize;
public int Size {
get { return mSize; }
set {
if (value < 0)
mSize = 0;
else
mSize = value;
}
}
shoe.Size++;登录后复制
|
| JavaStructsC# |
聽 No structs in Java. | struct StudentRecord {
public string name;
public float gpa;
public StudentRecord(string name, float gpa) {
this.name = name;
this.gpa = gpa;
}
}
StudentRecord stu = new StudentRecord("Bob", 3.5f);
StudentRecord stu2 = stu;
stu2.name = "Sue";
Console.WriteLine(stu.name); // Prints "Bob"
Console.WriteLine(stu2.name); // Prints "Sue"登录后复制
|
| JavaConsole I/OC# |
java.io.DataInput in = new java.io.DataInputStream(System.in);
System.out.print("What is your name? ");
String name = in.readLine();
System.out.print("How old are you? ");
int age = Integer.parseInt(in.readLine());
System.out.println(name + " is " + age + " years old.");
int c = System.in.read(); // Read single char
System.out.println(c); // Prints 65 if user enters "A"
// The studio costs $499.00 for 3 months.
System.out.printf("The %s costs $%.2f for %d months.%n", "studio", 499.0, 3);
// Today is 06/25/04
System.out.printf("Today is %tD\n", new java.util.Date());登录后复制
| Console.Write("What's your name? ");
string name = Console.ReadLine();
Console.Write("How old are you? ");
int age = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("{0} is {1} years old.", name, age);
// or
Console.WriteLine(name + " is " + age + " years old.");
int c = Console.Read(); // Read single char
Console.WriteLine(c); // Prints 65 if user enters "A"
// The studio costs $499.00 for 3 months.
Console.WriteLine("The {0} costs {1:C} for {2} months.\n", "studio", 499.0, 3);
// Today is 06/25/2004
Console.WriteLine("Today is " + DateTime.Now.ToShortDateString());登录后复制
|
| JavaFile I/OC# |
import java.io.*;
// Character stream writing
FileWriter writer = new FileWriter("c:\\myfile.txt");
writer.write("Out to file.\n");
writer.close();
// Character stream reading
FileReader reader = new FileReader("c:\\myfile.txt");
BufferedReader br = new BufferedReader(reader);
String line = br.readLine();
while (line != null) {
System.out.println(line);
line = br.readLine();
}
reader.close();
// Binary stream writing
FileOutputStream out = new FileOutputStream("c:\\myfile.dat");
out.write("Text data".getBytes());
out.write(123);
out.close();
// Binary stream reading
FileInputStream in = new FileInputStream("c:\\myfile.dat");
byte buff[] = new byte[9];
in.read(buff, 0, 9); // Read first 9 bytes into buff
String s = new String(buff);
int num = in.read(); // Next is 123
in.close();登录后复制
|
using System.IO;
// Character stream writing
StreamWriter writer = File.CreateText("c:\\myfile.txt");
writer.WriteLine("Out to file.");
writer.Close();
// Character stream reading
StreamReader reader = File.OpenText("c:\\myfile.txt");
string line = reader.ReadLine();
while (line != null) {
Console.WriteLine(line);
line = reader.ReadLine();
}
reader.Close();
// Binary stream writing
BinaryWriter out = new BinaryWriter(File.OpenWrite("c:\\myfile.dat"));
out.Write("Text data");
out.Write(123);
out.Close();
// Binary stream reading
BinaryReader in = new BinaryReader(File.OpenRead("c:\\myfile.dat"));
string s = in.ReadString();
int num = in.ReadInt32();
in.Close();登录后复制
|
