帮助搜索2D数组（Java）

Question

我完全迷失了。 我已经搜索了这个问题可能30分钟了，我找不到任何特定于Java的解决方案（或任何与java交叉的解决方案）。

我已经尝试使用通用的两个简单for循环来遍历每个单独的String，但是如果搜索项位于数组的第一列，它似乎只返回结果。

    public static String search(String term) {
        String result = "";
        int row = db.bookdb.length;

        for (int i=0; i<db.bookdb.length; i++) {
            for (int j=0; j<4; j++) {
                if (term.equals(db.bookdb[i][j])) {
                     row = i;
                     break;
                }
            }
        }

        if (row == db.bookdb.length) {
            result += "Your search failed to return any results";
        }
        else {
            for (int j=0; j<4; j++) {
                result += db.bookdb[row][j] + "    ";
            }
        }

        return result;
    }

db是我正在使用的对象，bookdb是所述对象中的2D数组。 （是的，列数总是4）

如果有任何其他信息，您可以随意询问。

Answer 1

你的搜索方法工作正常。 我创建了一个类并使用了你的搜索方法（复制和粘贴，我甚至没有更改你的搜索），它的工作原理。 这让我相信问题在于您输入数据的方式。

class Pdeuchler {

    static Pdeuchler db;

    String[][] bookdb;


    public static String search(String term) {
        String result = "";
        int row = db.bookdb.length;

        outer_loop: // CHANGE #1 added a named loop
        for (int i=0; i<db.bookdb.length; i++) {
            for (int j=0; j<4; j++) {
                if (term.equals(db.bookdb[i][j])) {
                     row = i;
                     //break; //REMOVED
                     break outer_loop; // CHANGE #2 breaking to the outer_loop
                }
            }
        }

        if (row == db.bookdb.length) {
            result += "Your search failed to return any results";
        }
        else {
            for (int j=0; j<4; j++) {
                result += db.bookdb[row][j] + "    ";
            }
        }

        return result;
    }

    public static void main(String[] args) {
        db = new Pdeuchler();
        db.bookdb = new String[10][4]; // title, author, publisher, year

        db.bookdb[0] = new String[] {"Awesome Book","Stan","West","2001"};
        db.bookdb[1] = new String[] {"Cool Story","Dan","North","2002"};
        db.bookdb[2] = new String[] {"Brothers","North","North","2003"};
        db.bookdb[3] = new String[] {"Never again!","Bob","West","2004"};
        db.bookdb[4] = new String[] {"Howdy Partner","Stan","South","2005"};
        db.bookdb[5] = new String[] {"What the StackOverflow?","Dan","North","2006"};
        db.bookdb[6] = new String[] {"That's hilarious","Angie","South","2007"};
        db.bookdb[7] = new String[] {"I like pie","Angie","East","2008"};
        db.bookdb[8] = new String[] {"Bob writes a book","Bob","South","2009"};
        db.bookdb[9] = new String[] {"The adverntures of Bob","Bob","North","2010"};

        System.out.println(search("I like pie"));
        System.out.println(search("North"));
        System.out.println(search("Dan"));
    }

}

结果如下：

C:\junk>java Pdeuchler
I like pie    Angie    East    2008
The adverntures of Bob    Bob    North    2010
What the StackOverflow?    Dan    North    2006

C:\junk>

以及改变的结果：

C:\junk>javac Pdeuchler.java

C:\junk>java Pdeuchler
I like pie    Angie    East    2008
Cool Story    Dan    North    2002
Cool Story    Dan    North    2002

C:\junk>

如果我们使用高级搜索方法（我称之为search2），我们会得到：

C:\junk>java Pdeuchler
simple search:
I like pie    Angie    East    2008
Cool Story    Dan    North    2002
Cool Story    Dan    North    2002

advanced search:
I like pie    Angie    East    2008

Cool Story    Dan    North    2002
Brothers    North    North    2003
What the StackOverflow?    Dan    North    2006
The adverntures of Bob    Bob    North    2010

Cool Story    Dan    North    2002
What the StackOverflow?    Dan    North    2006


C:\junk>

这是高级搜索方法：

public static String search2(String term) {
    String result = "";
    int row = db.bookdb.length;

    for (int i=0; i<db.bookdb.length; i++) {
        for (int j=0; j<4; j++) {
            if (term.equals(db.bookdb[i][j])) {
                 row = i;
                 for (int k=0; k<4; k++) {
                     result += db.bookdb[i][k] + "    ";
                 }
                 result += "\n";
                 break; // breaks out of the INNER (j) loop
            }
        }
    }

    if (row == db.bookdb.length) {
        result += "Your search failed to return any results";
    }
    return result;
}

Answer 2

你的“break”语句会突破内部循环而不是外部循环。 像这样重写：

boolean found = false;

for (int i = 0; i < db.bookdb.length && !found; i ++) {
  for (int j=0; j<4 && !found; j++) {
    if (yourCondition) {
      row = i;
      found = true;
    }
  }
}

Answer 3

你确定db.bookdb.length不总是1吗？

这可能对您有所帮助：

int [] [] matrix = new int [10] [30]; System.out.println（“行数=”+ matrix.length）; System.out.println（“列数=”+矩阵[0] .length）;

Answer 4

我不确定你的bookdb是什么类型，但你可以改变它

private static int searchTermInArray(String[][] bookdb, String term) {
    for (int i=0; i<bookdb.length; i++) {
        for (int j=0; j<4; j++) {
            if (term.equals(bookdb[i][j])) {
                return i;
            }
        }
    }
    return -1;
}

public static String search(String term) {
    String result = "";
    int row = searchTermInArray(db.bookdb, term);
    if (row == -1) {
        result += "Your search failed to return any results";
    }
    else {
        for (int j=0; j<4; j++) {
            result += db.bookdb[row][j] + "    ";
        }
    }

    return result;
}

Answer 5

你需要打破这两个循环。 您可以使用“mainfor”标记外部循环，并在中断后使用该标签

public static String search(String term) {
    String result = "";
    int row = db.bookdb.length;

    mainfor: for (int i=0; i<db.bookdb.length; i++) {
        for (int j=0; j<4; j++) {
            if (term.equals(db.bookdb[i][j])) {
                 row = i;
                 break mainfor;
            }
        }
    }
 ... //rest of your code as is
}