偶数
public class Sum { public static void main(String[] args) { // TODO Auto-generated method stub int sum=0; System.out.print("1到100的偶数:"); for(int i=1;i<=100;i++){ if(i%2==0){ sum=sum+i; System.out.print(i+","); } } System.out.println(" "); System.out.println("1到100偶数和为:"+sum); } }
输出结果:
1到100的偶数: 2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50, 52,54,56,58,60,62,64,66,68,70,72,74,76,78,80,82,84,86,88,90,92,94,96,98 ,100, 1 到 100 偶数和为:2550
字符串替换
public class TestStr { public static void main(String[] args) { String s = new String(); s = "aa:11|bb:22|cc:33"; System.out.println(s); //String sbf = s.toString().replaceAll(":", ","); //System.out.println(sbf); //String bf = sbf.replaceAll("\\|", ","); String bf=s.toString().replaceAll("\\|", ":"); System.out.println(bf); String[] strs = bf.split(":"); for (int i = 0; i < strs.length; i++) { System.out.print(strs[i]); //System.out.print(" "); } } }
输出结果:
aa:11|bb:22|cc:33 aa:11:bb:22:cc:33 aa11bb22cc33
素数
public class TestPrime { public static boolean isPrime(int num) { //System.out.println(Math.sqrt(num)); //System.out.println((int)Math.sqrt(num)); for(int i = 2; i <= (int)Math.sqrt(num); i++) {// 程序默认2是素数,当j=2时,循环不执行 if(num % i == 0) { return false; } } return true; } public static void main(String[] args){ for(int j = 2; j <= 100; j++) if(TestPrime.isPrime(j)) System.out.println(j + " is a prime"); } }
输出结果
2 is a prime 3 is a prime 5 is a prime 7 is a prime 11 is a prime 13 is a prime 17 is a prime 19 is a prime 23 is a prime 29 is a prime 31 is a prime 37 is a prime 41 is a prime 43 is a prime 47 is a prime 53 is a prime 59 is a prime 61 is a prime 67 is a prime 71 is a prime 73 is a prime 79 is a prime 83 is a prime 89 is a prime 97 is a prime
截串
编程:编写一个截取字符串的函数,输入为一个字符串和字节数,输出为按字节截取的字符串. 但是要保证汉字不被截半个,如"我 ABC"4,应该截为"我 AB",输入"我 ABC 汉 DEF",6,应 该输出为"我 ABC"而不是"我 ABC+汉的半个"
public class SplitString { String SplitStr; int SplitByte; public SplitString(String str, int bytes) { SplitStr = str; SplitByte = bytes; System.out.println("The String is:′" + SplitStr + "′;SplitBytes=" + SplitByte); } public void SplitIt() { int loopCount; loopCount = (SplitStr.length() % SplitByte == 0) ? (SplitStr.length() / SplitByte) : (SplitStr.length() / SplitByte + 1); System.out.println("Will Split into " + loopCount); for (int i = 1; i <= loopCount; i++) { if (i == loopCount) { System.out.println(SplitStr.substring((i - 1) * SplitByte, SplitStr.length())); } else { System.out.println(SplitStr.substring((i - 1) * SplitByte, (i * SplitByte))); } } } public static void main(String[] args) { SplitString ss = new SplitString( "test中dd文dsaf中男大3443n中国43中国人0ewldfls=103", 4); ss.SplitIt(); } }
输出:
The String is:′t
est中dd文dsaf中男大3443n中国43中国人 0ewldfls=103′;SplitBytes=4 Will Split into 10 test 中dd文 dsaf 中男大3 443n 中国43 中国人0 ewld fls= 103
字符串翻转
public class ReserveString { public static void main(String[] args) { String s = new String("abcde"); String st = ReserveString.reserve(s); System.out.println(st); } public static String reserve(String sti) { int len = sti.length(); StringBuffer sb = new StringBuffer(len); for (int i = len - 1; i >= 0; i--) sb.append(sti.charAt(i)); ret