java - 如何在共享一个共同值的多个二维数组之间进行迭代？

Question

如何在多个二维数组之间进行迭代。例如，我想查找居住在 Cobb、出生于 1970 年之后并且在 Evan Duggan 教授的类(class)中获得 C 或更好成绩的所有学生。这两个表共享用户 ID，例如“0033”

 public class JavaApplication2 {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {
    // TODO code application logic here
  String [ ][ ] students = {
                        { "0033", "Sandra", "Smith", "Cobb", "1989" },
                        { "1144", "Bo", "Harrison", "DeKalb","1987" },
                        { "2255", "Sam", "Mitchell", "Cobb", "1969"},
                        { "3366", "Sabrina", "Jones", "Cobb", "1979"},
                        { "4477", "Harry", "Johnson", "Cobb", "1982"},
                        { "5588", "Lisa", "Simpson", "Paulding", "1982"}
                        };

  String[ ][ ] grades = {
                        { "5588", "201405", "CSE", "1301J", "A", "Ian Salts" },
                        { "5588", "201405", "COMM", "2400","B", "Evan Duggan" },
                        { "5588", "201408", "CSE", "1302J", "A", "Ian Salts"},
                        { "0033", "201405", "CSE", "1301J", "C", "Ian Salts"},
                        { "0033", "201405", "COMM", "2400", "A", "Evan Duggan"}
                        };




       for (int i = 0; i < students.length; i++)
       {
              System.out.print(students[ i ] [ 0 ] + ": ");
              for (int j = 1; j < students[ i ].length; j++)
              {
                         System.out.print(students[ i ][ j ] + " ");
              }
             System.out.println( );
       }
         System.out.println( );
        for (int i = 0; i < grades.length; i++)
       {
              System.out.print(grades[ i ] [ 0 ] + ": ");
              for (int j = 1; j < grades[ i ].length; j++)
              {
                         System.out.print(grades[ i ][ j ] + " ");
              }
             System.out.println( );

       }

        for ( int i=0; i<grades.length; i++) {
            for(int j=0; j< grades[i].length; j++) {
    if ( grades[i][j].equals("A") && grades [i][5].equals("Evan Duggan")) {
        System.out.println("The student ID is "+ grades[i][0]);

    }
    else if ( grades[i][j].equals("B") && grades [i][5].equals("Evan Duggan")){
        System.out.println("The student ID is "+ grades[i][0]);
       }
    else if ( grades[i][j].equals("C") && grades [i][5].equals("Evan Duggan")){
        System.out.println("The student ID is "+ grades[i][0]);
    }

}


}

 }
 }       

Answer 1

假设您必须使用二维数组，您可以通过分组和匹配与每个数组相关的条件来解决此问题:

for (String[] student: students) {
   // First set of criteria relevant to students array
   if (student[3].equals("Cobb") && Integer.parseInt(student[4]) > 1970) {

       for (String[] grade: grades) {
          // Match on student id as well as criteria relevant to grades array
          if (grade[0].equals(student[0]) && grade[5].equals("Evan Duggan"))  {

             // I separate the conditionals here to keep it readable/tidy
             // Consider using a Enum type or comparator etc.
             if (grade[4].equals("C") || grade[4].equals("B") || grade[4].equals("A")) {
                // Code for handling matching student
             }
          }
       }
   }
}