lab 1 考点：
substring/concat/equals/equalsIgnoreCase/indexOf
all index from 0 not 1.
homework 1 考点：
opencommerical是老师上课讲过的例子，现学现卖／怎样读取网页检查元素／readline()会自动向下一个进行读取
1 class OpenCommerical {
2
3 /** Prompts the user for the name X of a company (a single string), opens
4 * the Web site corresponding to www.X.com, and prints the first five lines
5 * of the Web page in reverse order.
6 * @param arg is not used.
7 * @exception Exception thrown if there are any problems parsing the
8 * user‘s input or opening the connection.
9 */
10 public static void main(String[] arg) throws Exception {
11
12 BufferedReader keyboard;
13 String inputLine;
14
15 keyboard = new BufferedReader(new InputStreamReader(System.in));
16
17 System.out.print("Please enter the name of a company (without spaces): ");
18 System.out.flush(); /* Make sure the line is printed immediately. */
19 inputLine = keyboard.readLine();
20
21 /* Replace this comment with your solution. */
22 URL u = new URL("http://www."+inputLine+".com/");
23 InputStream ins = u.openStream();
24 InputStreamReader isr = new InputStreamReader(ins);
25 String[] FiveLines = new String[5];
26 BufferedReader Baidu = new BufferedReader(isr);
27 for(int i=0; i<5 ;i++){
28 FiveLines[i] = Baidu.readLine();
29 }
30 for(int j=4;j>=0;j--){
31 System.out.println(FiveLines[j]);
32 }
33 }
34 }
nuke2 substring运用
lab2 考点
gcd辗转相除
static private int gcd (int x, int y) { //辗转相除法
/* Replace the following line with your solution. */
if(y==0)
return x;
else
return gcd(y,x%y);
}
构造函数
System.out.println("..." + d1);//这里d1会自动调用toString(); 可以不用写出来。
1 class Fraction {
2
3 /* private fields within a Fraction. */
4 static private int numberOfFractions = 0;
5
6 private int numerator;
7 private int denominator;
8
9 /** Constructs a Fraction n/d.
10 * @param n is the numerator. Must be nonnegative.
11 * @param d is the denominator. Must be positive.
12 */
13 public Fraction(int n, int d) {
14 if (n < 0) {
15 System.out.println("Fatal error: Negative numerator.");
16 System.exit(0);
17 }
18 if (d < 1) {
19 System.out.println("Fatal error: Non-positive denominator.");
20 System.exit(0);
21 }
22 numberOfFractions++;
23 numerator = n;
24 denominator = d;
25 }
26
27 /** Constructs a Fraction n/1.
28 * @param n is the numerator. Must be nonnegative.
29 */
30 public Fraction(int n) {
31 this(n, 1); //call the two-parameters constructor
32 }
33
34 /** Constructs a Fraction 0/1.
35 */
36 public Fraction() {
37 this(0,1); // call the two-parameters constructor
38 }
39
40 /** Copies the Fraction "original".
41 */
42 public Fraction(Fraction original) {
43 this(original.numerator,original.denominator);
44 }
45
46 /** Converts this Fraction to a string format: "numerator/denominator."
47 * Fractions should be printed in reduced form (part of your assignment is
48 * to make this true).
49 * @return a String representation of this Fraction.
50 */
51 public String toString() {
52 int thisGcd = gcd(numerator, denominator);
53
54 return (numerator / thisGcd + "/" + denominator / thisGcd);
55 }
56
57 /** Return the sum of two fractions.
58 * @param f2 is the Fraction to be added.
59 * @return the result of adding f2 to this Fraction.
60 */
61 public Fraction add(Fraction f2) {
62 Fraction r = new Fraction((numerator * f2.denominator) +
63 (f2.numerator * denominator),
64 denominator * f2.denominator);
65 return r;
66 }
67
68 /** Replaces this Fraction‘s numerator with a new value.
69 * @param numerator is the new numerator. Must be nonnegative.
70 */
71 public void changeNumerator(int numerator) { // DO NOT CHANGE THIS SIGNATURE!
72 // Fix the bug that prevents this method from working correctly.
73 if (numerator < 0) {
74 System.out.println("Fatal error: Negative numerator.");
75 System.exit(0);
76 }
77 this.numerator = numerator;
78
79 }
80
81 /** Returns the number of Fraction objects in existence.
82 * @return the number of Fraction objects in existence.
83 */
84 public int fracs() { // DO NOT CHANGE THIS SIGNATURE!
85 // Fix the bug that prevents this method from working correctly.
86 return numberOfFractions;
87 }
88
89 /** Computes the greatest common divisor (gcd) of the two inputs.
90 * @param x must be nonnegative
91 * @param y must be nonnegative
92 * @return the gcd of x and y
93 */
94 static private int gcd (int x, int y) { //辗转相除法
95 /* Replace the following line with your solution. */
96 if(y==0)
97 return x;
98 else
99 return gcd(y,x%y);
100 }
101
102 /** Put the Fraction class through some tests.
103 * @param argv is not used.
104 */
105 public static void main(String[] argv) {
106
107 /* Test all four contructors and toString. */
108 Fraction f0 = new Fraction(0,1);
109 Fraction f1 = new Fraction(3);
110 Fraction f2 = new Fraction(12, 20);
111 Fraction f3 = new Fraction(f2);
112
113 System.out.println("\nTesting constructors and toString():");
114 System.out.println("The fraction f0 is " + f0.toString());
115 System.out.println("The fraction f1 is " + f1); // toString is implicit.
116 System.out.println("The fraction f2 is " + f2);
117 System.out.println("The fraction f3 is " + f3 + ", which should equal f2");
118
119 /* Test the add method. */
120 System.out.println("\nTesting add:");
121
122
123
124 Fraction sumOfTwo = f1.add(f2); // Sum of f1 and f2.
125 Fraction sumOfThree = f0.add(f1).add(f2); // Sum of f0, f1, and f2.
126
127 System.out.println("The sum of " + f1 + " and " + f2 + " is " + sumOfTwo);
128 System.out.println("The sum of " + f0 + ", " + f1 + " and " + f2 + " is " +
129 sumOfThree);
130
131
132 /* Test the methods used in Part III. */
133 System.out.println("\nTesting changeNumerator and fracs:");
134
135 f3.changeNumerator(7);
136 System.out.println("Now f3 is " + f3 + ", which should be 7/20");
137 System.out.println("The total number of Fraction objects is " +
138 f3.fracs());
139
140 /* Test gcd function (static method). */
141 System.out.println("\nTesting gcd:");
142 System.out.println("The gcd of 2 and 10 is: " + gcd(2, 10));
143 System.out.println("The gcd of 15 and 5 is: " + gcd(15, 5));
144 System.out.println("The gcd of 24 and 18 is: " + gcd(24, 18));
145 System.out.println("The gcd of 10 and 10 is: " + gcd(10, 10));
146 System.out.println("The gcd of 21 and 400 is: " + gcd(21, 400));
147 }
148 }
homework2考点
闰年判断
public static boolean isLeapYear(int year) {
if((year%4==0&&year%100!=0)||(year%400==0)){
return true;
}else return false; // replace this line with your solution
}
正则表达+split分割字符串+Integer.parseInt()方法将String转化为int
public Date(String s) {
if(s.matches("\\d{1,2}\\/\\d{1,2}\\/\\d{1,4}")){
String[] d=s.split("/");
month=Integer.parseInt(d[0]);
day=Integer.parseInt(d[1]);
year=Integer.parseInt(d[2]);
}else System.exit(0);
}
string int 相互转换知识补充
http://blog.csdn.net/memray/article/details/7312817/ 转自MemRay博客
String ==》int
1). int i = Integer.parseInt([String]); 或
i = Integer.parseInt([String],[int radix]);
2). int i = Integer.valueOf(my_str).intValue();
int ==》String
1.) String s = String.valueOf(i);
2.) String s = Integer.toString(i);
3.) String s = "" + i;
注: Double, Float, Long 转成字串的方法大同小异.
未完......................
时间： 2024-10-29 12:57:15