第1关 String类的常用方法
package step1;public class StringExample {public static void main(String args[]) { /********* Begin *********/String s1 = new String("you are a student"), s2 = new String("how are you");if (s1.equals(s2)) // 使用equals方法判断s1与s2是否相同{System.out.println("s1与s2相同");} else {System.out.println("s1与s2不相同");}String s3 = new String("22030219851022024");if (s3.startsWith("220302")) // 判断s3的前缀是否是“220302”{System.out.println("吉林省的身份证");}String s4 = new String("你"), s5 = new String("我");if (s4.compareTo(s5) > 0)// 按着字典序s4大于s5的表达式{System.out.println("按字典序s4大于s5");} else {System.out.println("按字典序s4小于s5");}int position = 0;String path = "c:\\java\\jsp\\A.java";position = path.lastIndexOf("\\"); // 获取path中最后出现\\的位置System.out.println("c:\\java\\jsp\\A.java中最后出现\\的位置:" + position);String fileName = path.substring(path.lastIndexOf("\\") + 1); // 获取path中“A.java”子字符串System.out.println("c:\\java\\jsp\\A.java中含有的文件名:" + fileName);String s6 = new String("100"), s7 = new String("123.678");int n1 = Integer.parseInt(s6); // 将s6转化成int型数据double n2 = Double.parseDouble(s7); // 将s7转化成double型数据double m = n1 + n2;System.out.println(m);String s8 = String.valueOf(m); // String调用valueOf(m)方法将m转化为字符串对象position = s8.indexOf(".");String temp = s8.substring(position + 1); // 获取s8中小数点后面的小数System.out.println("数字" + m + "有" + temp.length() + "位小数");String s9 = new String("ABCDEF");char a[] = s9.toCharArray(); // 将s9存放到数组a中for (int i = a.length - 1; i >= 0; i--) {System.out.print(" " + a[i]);} /********* End *********/}}第2关 矩阵转置
package step2;import java.util.Scanner;public class SwapMatrix {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int[][] matrix = new int[3][3];for (int i = 0; i < 3; i++) {for (int j = 0; j < 3; j++) {matrix[i][j] = scanner.nextInt();}} /********** Begin **********/System.out.println("原始数组为：");for (int i = 0; i < 3; i++) {for (int j = 0; j < 3; j++) {System.out.print(matrix[i][j] + " ");}System.out.println();}int[][] transposedMatrix = new int[3][3];for (int i = 0; i < 3; i++) {for (int j = 0; j < 3; j++) {transposedMatrix[i][j] = matrix[j][i];}}System.out.println("行列互调后数组为：");for (int i = 0; i < 3; i++) {for (int j = 0; j < 3; j++) {System.out.print(transposedMatrix[i][j] + " ");}System.out.println();} /********** End **********/scanner.close();}}第3关 求平均分及各个区间段的人数
package step3;import java.util.Scanner;public class Score {public static void main(String args[]) {Scanner scanner = new Scanner(System.in);/********** Begin **********/ int excellent = 0; // 优秀人数 int good = 0; // 良好人数 int medium = 0; // 中等人数 int pass = 0; // 及格人数 int fail = 0; // 不及格人数 double sum = 0; // 总成绩 double score; // 学生成绩 int count = 0; // 学生总人数 while (true) { score = scanner.nextDouble(); if (score == -1) { break; } count++; sum += score; if (score >= 90) { excellent++; } else if (score >= 80) { good++; } else if (score >= 70) { medium++; } else if (score >= 60) { pass++; } else { fail++; } } System.out.println("不及格的人数为：" + fail); System.out.println("及格的人数为：" + pass); System.out.println("中等的人数为：" + medium); System.out.println("良好的人数为：" + good); System.out.println("优秀的人数为：" + excellent); System.out.printf("全班平均分为：%.1f\n", sum / count); /********** End **********/scanner.close();}}