Java OOP类矩阵方法等于

-1

更新：当我检查两个矩阵是否相等时，我的程序总是返回false。初始化和复制工作正常，我可以通过控制台验证两个矩阵在打印后是否相同。不管我做什么，equals方法总是返回false！Java OOP类矩阵方法等于

// Class Matrix (Matrix.java) 
import java.util.Scanner; 
import java.util.Random; 

public class Matrix { 
private int size; 
private int[][] table = new int[MAX][MAX]; 


//Default constructor 
public Matrix() { 
size = 0; 
} 

//Alternate constructor 
public Matrix(int s) { 
size = s; 
} 

//Method to initiate a matrix with random values 
    public void init(int low, int up) { 
    Random rand = new Random(); 
    for (int r = 0; r < size; r++) { 
     for (int c = 0; c < size; c++) 
     table[r][c] = rand.nextInt(up - low + 1) + low; 
    } 
    } 

//Method to copy the matrix 
public void copy(Matrix a) { 
    for (int r = 0; r < size; r++) { 
    for (int c = 0; c < size; c++) 
     table[r][c] = a.table[r][c]; 
    } 
} 

//Method to compare two matrices for equality 
    public boolean equals(Object obj) { 
    boolean result = false; 
    if (obj instanceof Matrix) { 
     Matrix otherMatrix = (Matrix) obj; 
     for (int r = 0; r < size; r++) { 
     for (int c = 0; c < size; c++) 
      //problem solved! 
      //previous: 
      //result = (table[r] == otherMatrix.table[r] && table[c] == otherMatrix.table[c]); 
      //fixed 
      result = (table[r][c] == otherMatrix.table[r][c]); 
     } 
    } 
    return result; 
    }

客户端来进行测试：

first.init(LOW, UP); 
System.out.println("The original matrix is:"); 
first.print(); 
System.out.println("The copy of this matrix is: "); 
result.copy(first); 
result.print(); 
System.out.println("Testing for equality. Should be equal!!"); 
if (result.equals(first)) 
    System.out.println("The matrices are equal!!"); 
else 
    System.out.println("The matrices are NOT equal!!");

来源

2016-03-03 Steven

如果'size'是零？另外，我认为你可能想重新考虑你的循环中的逻辑（你的内循环只会在返回之前运行一次）。 – ajshort

您的for可以运行0次，然后不返回语句 – DDan

用默认false初始化一个布尔值，如有必要，更改它并最终返回它。你在循环中返回一个值，但循环可能永远不会开始。 –

public boolean equals(Object obj) { 
    boolean match = false; 
    if (obj instanceof Matrix) { 
    Matrix otherMatrix = (Matrix) obj; 
    for (int r = 0; r < size; r++) { 
     for (int c = 0; c < size; c++) 
     match = (table[r] == otherMatrix.table[r] && table[c] == otherMatrix.table[c]); 
    } 
    } 
    return match ; 
}

来源

2016-03-03 03:04:06

for周期可以运行0次，这会产生没有return语句。你可以更新到这样的东西。

public boolean equals(Object obj) { 
    boolean result = false; 
    if (obj instanceof Matrix) { 
      Matrix otherMatrix = (Matrix) obj; 
      // I copied your logic here, are you sure it is correct? --> 
      for (int r = 0; r < size; r++) { 
       for (int c = 0; c < size; c++) 
       result = table[r] == otherMatrix.table[r] && table[c] == otherMatrix.table[c]; 
      } 
      // <-- 
    } 
    return result; 
} 

// testing part removed, because lack of context

来源

2016-03-03 03:17:06 DDan

不会运行零时间，因为在输入此方法之前已经输入验证以确保大小大于0.我不确定是否现在要指责我的客户，但我总是得到虚假的回报。看到上面的评论客户端 – Steven

我明白，但编译器可能不是。编译器不能总是检查代码的上下文，以确保它可以运行。（虽然他们正在变得更好）。然而根据定义'for'循环可以运行0次。这就是编译器所看到的，这就是它抛出错误的原因。 – DDan

我更新了您的客户端测试 – DDan

修正我的计划，我要真诚地感谢你的帮助:)当我检查两个矩阵的相等

我的程序总是返回false。初始化和复制工作正常，我可以通过控制台验证两个矩阵在打印后是否相同。不管我做什么，equals方法总是返回false！

// Class Matrix (Matrix.java) 
import java.util.Scanner; 
import java.util.Random; 

public class Matrix { 
private int size; 
private int[][] table = new int[MAX][MAX]; 


//Default constructor 
public Matrix() { 
size = 0; 
} 

//Alternate constructor 
public Matrix(int s) { 
size = s; 
} 

//Method to initiate a matrix with random values 
    public void init(int low, int up) { 
    Random rand = new Random(); 
    for (int r = 0; r < size; r++) { 
     for (int c = 0; c < size; c++) 
     table[r][c] = rand.nextInt(up - low + 1) + low; 
    } 
    } 

//Method to copy the matrix 
public void copy(Matrix a) { 
    for (int r = 0; r < size; r++) { 
    for (int c = 0; c < size; c++) 
     table[r][c] = a.table[r][c]; 
    } 
} 

//Method to compare two matrices for equality 
    public boolean equals(Object obj) { 
    boolean result = false; 
    if (obj instanceof Matrix) { 
     Matrix otherMatrix = (Matrix) obj; 
     for (int r = 0; r < size; r++) { 
     for (int c = 0; c < size; c++) 
      //problem solved! 
      //previous: 
      //result = (table[r] == otherMatrix.table[r] && table[c] == otherMatrix.table[c]); 
      //fixed 
      result = (table[r][c] == otherMatrix.table[r][c]); 
     } 
    } 
    return result; 
    }

客户端来进行测试：

first.init(LOW, UP); 
System.out.println("The original matrix is:"); 
first.print(); 
System.out.println("The copy of this matrix is: "); 
result.copy(first); 
result.print(); 
System.out.println("Testing for equality. Should be equal!!"); 
if (result.equals(first)) 
    System.out.println("The matrices are equal!!"); 
else 
    System.out.println("The matrices are NOT equal!!");

来源

2016-03-03 04:20:28 Steven

Java OOP类矩阵方法等于

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