我编写了一系列矩阵运算，其中我采用二维浮点数组，将其视为矩阵，并对其执行矩阵运算以获取逆运算。我的问题是虽然我使用类方法的数组不是类的一部分，但每次我以数组作为参数运行方法时，数组本身也会被修改。
首先，我将描述如何得到矩阵的逆，然后我将显示输出。
采用矩阵的逆矩阵的步骤如下：
现在我将介绍实现这些操作的代码。为了简明起见，我不会描述如何获得未成年人矩阵或行列式，但我遇到的问题无论如何都会变得明显。
public class MatrixOperations {
//Note: this method works fine. There are no problems.
public float determinant(float [][] a)
{
float [][] temp_mat;
float res = 0;
//assuming a square matrix
/*If it's a 2X2, then use the formula for a determinant of
2X2 matrices.*/
if(a.length == 2)
{
return a[0][0]*a[1][1]-a[0][1]*a[1][0];
}
/*Otherwise do the determinant formula recursively until your
determinant is made up of 2X2 matrix determinants and scalar products*/
else
{
temp_mat = new float[a.length-1][a.length-1];
int placej = 0;
int placei = 0;
for(int k = 0; k<a.length;k++)
{
for(int j = 0; j<a.length; j++)
{
for(int i = 1; i < a.length; i++)
{
placei = i-1;
if(j != k)
{
if(j < k)
{
temp_mat[placei][j] = a[i][j];
}
else if(j > k)
{
if (i == 1){
placej = j-1;
}
temp_mat[placei][placej] = a[i][j];
}
}
}
}
res+=a[0][k]*determinant(temp_mat)*(int)Math.pow(-1, k);
}
return res;
}
}
//Note: this method also works fine
//Scalar product method
public float[][] mul(float[][] m, float r)
{
float[][] res = new float[m.length][m.length];
for(int i = 0; i < m.length; i++)
{
for(int j = 0; j < m.length; j++)
{
res[i][j]= m[i][j]*r;
}
}
return res;
}
//Note: This method also works fine
public float[][] mul(float[][] m,float[][] n)
{
float[][] res = new float[m.length][m.length];
for(int i = 0; i < m.length; i++)
{
for(int j = 0; j < m.length; j++)
{
for(int k = 0; k < m.length; k++)
{
res[i][j] += m[i][k]*m[k][i];
}
}
}
return res;
}
//The method for creating a matrix of minors
//Here I start having problems
public float[][] minor(float [][] m)
{
float [][] minor_mat = new float [m.length][m.length];
//If the matrix is greater than a 2X2, use this to generate a matrix of minors
if(m.length > 2)
{
float [][] current_minor = new float [m.length-1][m.length-1];
int placei = 0;
int placej = 0;
for(int i = 0; i < m.length; i++)
{
for(int j = 0; j < m.length; j++)
{
for(int k = 0; k < m.length; k++)
{
for(int l = 0; l < m.length; l++)
{
if(i != k && j != l)
{
if(k<i)
placei = k;
else if(k>i)
placei = k-1;
if(l<j)
placej = l;
else if(l>j)
placej = l-1;
current_minor[placei][placej] = m[k][l];
}
}
}
minor_mat[i][j] = this.determinant(current_minor);
}
}
}
//otherwise use the definition for 2X2 matrix of minors
else
{
//even though minor_mat is using m.clone() rather than m, when I return the result, m has still been modified for some reason.
minor_mat = m.clone()
float temp;
temp = minor_mat[0][0];
minor_mat[0][0] = minor_mat[1][1];
minor_mat[1][1] = temp;
temp = minor_mat[0][1];
minor_mat[0][1] = minor_mat[1][0];
minor_mat[1][0] = temp;
}
return minor_mat;
}
//the same problem occurs here as it did in the minor method
//m appears to get modified even though I only use m.clone()
public float[][] cofactor(float [][] m)
{
float[][] res = m.clone();
res = this.minor(res)
for(int i = 0; i < m.length; i++)
{
for(int j = 0; j < m.length; j++)
{
res[i][j] = res[i][j]*(int)Math.pow(-1, i + j);
}
}
return res;
}
//The following transpose, adjugate, and inverse methods have the same problem
public float[][] transpose(float[][] m)
{
float[][] res = new float[m.length][m.length];
float temp = 0;
for(int i = 0; i < m.length; i++)
{
for(int j = 0; j < m.length; j++)
{
temp = m[i][j];
res[i][j] = m[j][i];
res[j][i] = temp;
}
}
return res;
}
public float[][] adjugate(float[][] m)
{
float[][] res = this.transpose(this.cofactor(m));
return res;
}
public float[][] inverse(float[][] m)
{
float[][] res = this.mul(this.adjugate(m), (1/this.determinant(m)));
return res;
}
//print out the matrix in square form
public void matrixprint(float [][] m)
{
for(int i = 0; i < m.length; i++)
{
System.out.println("");
for(int j = 0; j < m[i].length; j++){
System.out.print(m[i][j] + " ");
}
}
System.out.println("\n");
}
}
现在是创建MatrixOperations类实例并在2X2矩阵上使用其方法的主类和main方法。
public class Main {
public static void main(String[] args) {
MatrixOperations mo = new MatrixOperations();
//Create a 2X2 matrix called "matrix" and set its elements
//Then perform each step on "matrix" and finally test if you have acquired the correct inverse
float [][] matrix = new float[2][2];
matrix[0][0] = 2;
matrix [0][1] = 5;
matrix [1][0] = 4;
matrix [1][1] = 3;
System.out.println("Matrix = ");
mo.matrixprint(matrix);
System.out.println("Minor = ");
mo.matrixprint(mo.minor(matrix));
System.out.println("Matrix = ");
mo.matrixprint(matrix);
System.out.println("Cofactor = ");
mo.matrixprint(mo.cofactor(matrix));
System.out.println("Matrix = ");
mo.matrixprint(matrix);
System.out.println("Adjugate = ");
mo.matrixprint(mo.adjugate(matrix));
System.out.println("Matrix = ");
mo.matrixprint(matrix);
System.out.println("Determinant = ");
System.out.println(mo.determinant(matrix));
System.out.println("Matrix = ");
mo.matrixprint(matrix);
System.out.println("Inverse = ");
mo.matrixprint(mo.inverse(matrix));
System.out.println("Matrix = ");
mo.matrixprint(matrix);
System.out.println("Identity = ");
mo.matrixprint(mo.mul(mo.inverse(matrix), matrix));
}
}
现在您将看到，当我显示输出时，每次在“矩阵”上使用方法，并重新打印“矩阵”时，“矩阵”本身已被修改，即使我的方法仅使用“矩阵”的副本而不是“矩阵”本身。
输出：
Matrix =
2.0 5.0
4.0 3.0
Minor =
3.0 4.0
5.0 2.0
Matrix =
3.0 4.0
5.0 2.0
Cofactor =
3.0 -4.0
-5.0 2.0
Matrix =
3.0 -4.0
-5.0 2.0
Adjugate =
3.0 5.0
4.0 2.0
Matrix =
3.0 4.0
5.0 2.0
Determinant =
-14.0
Matrix =
3.0 4.0
5.0 2.0
Inverse =
-0.21428573 0.35714287
0.2857143 -0.14285715
Matrix =
3.0 -4.0
-5.0 2.0
Identity =
0.1479592 0.1479592
0.12244898 0.12244898
任何帮助/解释为什么会发生这种情况将不胜感激。
答案 0 :(得分：0)
这是因为你在MatrixOperations类的方法中传递matrix对象的引用。它不是function setCookie(name, value) {
var cookie = name + "=" + escape(value) + ";";
document.cookie = cookie;
}
$("#form1").submit(function(){
setCookie("input1", $("#input1").val()); // do this for all inputs
});
对象的副本。
来自Java doc：
也会传入参考数据类型参数，例如对象 方法的价值。这意味着当方法返回时， 传入引用仍然引用与以前相同的对象。
答案 1 :(得分：0)
二维数组只是一个数组数组。
数组上的 <script>
$(document).ready(function() {
var max_fields = 10; //maximum input boxes allowed
var wrapper = $(".dynamicinput"); //Fields wrapper
var add_button = $(".add-more"); //Add button ID
var x = 1; //initlal text box count
$(add_button).click(function(e){ //on add input button click
e.preventDefault();
if(x < max_fields){ //max input box allowed
x++; //text box increment
$(wrapper).append('<div class="col-md-4 col1"><div class="form-group"><label for="exampleInputEmail1"><strong>Name *</strong></label><input type="text" class="form-control textwidth" id="PersonalssDetails_firstname" class="AssignedEmergencyContacts_Name" name="AssignedEmergencyContacts_Name[]"><span><a href="#" class="remove_field">Remove</a></div>');
$(wrapper).append('<div class="col-md-4 col2"><div class="form-group"><label for="exampleInputEmail1"><strong>Relationship *</strong></label><input type="text" class="form-control textwidth" id="AssignedEmergencyContacts_Relationship" class="AssignedEmergencyContacts_Relationship" name="AssignedEmergencyContacts_Relationship[]"><span><a href="#" class="remove_field1">Remove</a></div>');
$(wrapper).append('<div class="col-md-4 col3"><div class="form-group"><label for="exampleInputEmail1"><strong>Home Telephone*</strong></label><input type="text" class="form-control textwidth" id="AssignedEmergencyContacts_HomeTelephone" class="AssignedEmergencyContacts_HomeTelephone" name="AssignedEmergencyContacts_HomeTelephone[]"><span><a href="#" class="remove_field2">Remove</a></div>');
$(wrapper).append('<div class="col-md-4 col4"><div class="form-group"><label for="exampleInputEmail1"><strong>Mobile *</strong></label><input type="text" class="form-control textwidth" id="AssignedEmergencyContacts_Mobile" class="AssignedEmergencyContacts_Mobile" name="AssignedEmergencyContacts_Mobile[]"><span><a href="#" class="remove_field3">Remove</a></div>');
$(wrapper).append('<div class="col-md-4 col5"><div class="form-group"><label for="exampleInputEmail1"><strong>Work Telephone *</strong></label><input type="text" class="form-control textwidth" id="AssignedEmergencyContacts_WorkTelephone" class="AssignedEmergencyContacts_WorkTelephone" name="AssignedEmergencyContacts_WorkTelephone[]"><span><a href="#" class="remove_field4">Remove</a></div>');
}
});
$(wrapper).on("click",".remove_field", function(e){ //user click on remove text
e.preventDefault(); $(this).parent('div').remove(); x--;
})
});
</script>
<div class="col-md-4">
<div class="form-group">
<label for="exampleInputEmail1"><strong>Name *</strong></label>
<input type="text" class="form-control textwidth" id="PersonalssDetails_firstname" class="AssignedEmergencyContacts_Name" name="AssignedEmergencyContacts_Name[]"><span>
</div>
</div>
<div class="col-md-4">
<div class="form-group">
<label for="exampleInputEmail1"><strong>Relationship *</strong></label>
<input type="text" class="form-control textwidth" id="AssignedEmergencyContacts_Relationship" class="AssignedEmergencyContacts_Relationship" name="AssignedEmergencyContacts_Relationship[]"><span>
</div>
</div>
<div class="col-md-4">
<div class="form-group">
<label for="exampleInputEmail1"><strong>Home Telephone* </strong></label>
<input type="text" class="form-control textwidth" id="AssignedEmergencyContacts_HomeTelephone" class="AssignedEmergencyContacts_HomeTelephone" name="AssignedEmergencyContacts_HomeTelephone[]"><span>
</div>
</div>
<div class="col-md-4">
<div class="form-group">
<label for="exampleInputEmail1"><strong>Mobile * </strong></label>
<input type="text" class="form-control textwidth" id="AssignedEmergencyContacts_Mobile" class="AssignedEmergencyContacts_Mobile" name="AssignedEmergencyContacts_Mobile[]"><span>
</div>
</div>
<div class="col-md-4">
<div class="form-group">
<label for="exampleInputEmail1"><strong>Work Telephone * </strong></label>
<input type="text" class="form-control textwidth" id="AssignedEmergencyContacts_WorkTelephone" class="AssignedEmergencyContacts_WorkTelephone" name="AssignedEmergencyContacts_WorkTelephone[]"><span>
</div>
</div>
<div id="dynamicinput" class="dynamicinput">
</div>
只做一个浅层克隆。
所以你有一个新的克隆外部数组，但它引用相同的条目（内部数组）。
克隆外部数组后，遍历外部数组并克隆所有内部数组以获得深度克隆。