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Question

新

BigDecimal i = BigDecimal.ZERO;
for (int row = 0; row < testMark.length; row++) {
    for (int col = 0; col < testMark[row].length; col++) {
        i.add(new BigDecimal(testMark[row][col]));
    }
}
i.divide(new BigDecimal(60D));
outPut.setText(i.toString());`

OLD

查看代码的底部。我想将整个classAver字符串除以outPut.setText（classAver / 60）;

数组double[][] testMark = new double[15][4];

String classAver = "";
        for(int i=0; i < rowNumber; i++){
            classAver += ((testMark[0][0] + testMark[0][1] + testMark[0][2] + testMark[0][3])
                   +
                   (testMark[1][0] + testMark[1][1] + testMark[1][2] + testMark[1][3]) +
                   (testMark[2][0] + testMark[2][1] + testMark[2][2] + testMark[2][3]) +
                   (testMark[3][0] + testMark[3][1] + testMark[3][2] + testMark[3][3]) +
                   (testMark[4][0] + testMark[4][1] + testMark[4][2] + testMark[4][3]) +
                   (testMark[5][0] + testMark[5][1] + testMark[5][2] + testMark[5][3]) +
                   (testMark[6][0] + testMark[6][1] + testMark[6][2] + testMark[6][3]) +
                   (testMark[7][0] + testMark[7][1] + testMark[7][2] + testMark[7][3]) +
                   (testMark[8][0] + testMark[8][1] + testMark[8][2] + testMark[8][3]) +
                   (testMark[9][0] + testMark[9][1] + testMark[9][2] + testMark[9][3]) +
                   (testMark[10][0] + testMark[10][1] + testMark[10][2] + testMark[10][3]) +
                   (testMark[11][0] + testMark[11][1] + testMark[11][2] + testMark[11][3]) +
                   (testMark[12][0] + testMark[12][1] + testMark[12][2] + testMark[12][3]) +
                   (testMark[13][0] + testMark[13][1] + testMark[13][2] + testMark[13][3]) +
                   (testMark[14][0] + testMark[14][1] + testMark[14][2] + testMark[14][3]));
        }
outPut.setText(classAver); // <--How do I divide that number by 60?

Answer 1

修改

看到你指定的数组是double[15][4]，你可以使用它：

BigDecimal i = BigDecimal.ZERO;
for (int row = 0; row < testMark.length; row++) {
    for (int col = 0; col < testMark[row].length; col++) {
        i = i.add(new BigDecimal(testMark[row][col]));
    }
}
i = i.divide(new BigDecimal(60D));
outPut.setText(i.toString());

如果你想获得超过60个结果的平均值，那么在未来的路上：

BigDecimal i = BigDecimal.ZERO;
int count = 0;
for (int row = 0; row < testMark.length; row++) {
    for (int col = 0; col < testMark[row].length; col++, count++) {
        i = i.add(new BigDecimal(testMark[row][col]));
    }
}
i = i.divide(new BigDecimal(count));
outPut.setText(i.toString());

旧答案

Lordy，从哪里开始。

首先，循环：

for (int row = 0; row < 15; row++) { // these don't need to be concrete numbers ("15"), can be your array length
    for (int col = 0; col < 4; col++) {
        //append testMark[row][col]
    }
}

其次，使用StringBuilder，不要在循环中附加字符串

StringBuilder sb = new StringBuilder();
for (int row = 0; row < 15; row++) {
    for (int col = 0; col < 4; col++) {
        sb.append(testMark[row][col]); //can append delimiters, etc
    }
}
String value = sb.toString(); //Your complete value

然后，施展你的价值：

BigInteger i = BigInteger.valueOf(classAver); //returns an int value
i = i.divide(new BigInteger(60));
outPut.setText(i.toString());

如果您不想将值添加为字符串，可以将它们添加为数字：

BigInteger i = BigInteger.ZERO;
for (int row = 0; row < 15; row++) {
    for (int col = 0; col < 4; col++) {
        try {
            int raw = Integer.parseInt(testMark[row][col]);
            i = i.add(new BigInteger(raw));
        } catch (NumberFormatException ex) {
            System.err.println(String.format("Bad value caught! (Row: %d, Col: %d)", row, col));
        }
    }
}
i = i.divide(new BigInteger(60));
outPut.setText(i.toString());

Answer 2

根据您的更新，我认为您需要这样的内容 -

double[][] testMark = new double[15][4];
double total = 0; // start at 0.
double count = 0; // keep count.
for (int i = 0; i < testMark.length; i++) {
    // iterate the inner array.
    for (double d : testMark[i]) {
        total += d; // add it to the total.
        count++;    // add one to the count.
    }
}
String classAver = String.valueOf(total / count); // take average (as a String).
outPut.setText(classAver); // Set the text.

Answer 3

classAver不会保留您认为的价值。当你写

 for(int i=0; i < rowNumber; i++){
     classAver += [some long calculation that really needs to be done with loops];
 }

等同于

 for(int i=0; i < rowNumber; i++){
     classAver = classAver + ...; 
 }

当您在+上使用String时，程序会将任何非String个操作数转换为String，并连接字符串。因此，如果您有5行并且您的计算产生1001,2001,3001,4001和5001，则生成的classAver将不是"15005"，而是"10012001300140015001"。（P.S.现在我知道它是double，这会让事情变得更糟，因为你最终可能会出现像"1001.02001.03001.04001.05001.0"这样的乱码。）

道德：当您进行计算时，请使用数字类型（int，long，double，BigInteger等。不要使用String。完成计算后，如果您需要String，然后转换它，例如：

double classAver;

[compute classAver] 

outPut.setText(Double.toString(classAver));  // or Integer.toString(n) for integers

或

outPut.setText("" + classAver);

Java - 如何用数字划分字符串？

3 个答案:

修改

旧答案