"illegal start of type" & "class, interface or enum expected"

Question

当我编译以下java代码时，它会抛出illegal start of type&class, interface or enum expected错误。

在下面代码中的Persolation类中，声明了属于另一个类的WeightedQuickUnionUF数据类型。WeightedQuickUnionUF类存储在当前工作目录中一个名为"algs4.jar"的jar文件中。

我已经检查了好几次代码，但都找不到缺陷，完全卡住了。

代码如下：

public class Percolation{
    public static Percolation(int n){
        boolean[][] A=new boolean[n][n];
    }
    int i,j;
    WeightedQuickUnionUF WQUF=new WeightedQuickUnionUF[n*n+2];
    for(i=1;i<=n;i++)
    {
        WQUF.union(0,i);
    }
    for (i=n*n-n+1;i<=n*n;i++)
    {
        WQUF.union(n*n+1,i);
    }
    do {
        i=StdRandom.uniform(n-1)+1;
        j=StdRandom.uniform(n-1)+1;
    } while(A[i][j]!=0)
    open(i,j);
    private static int xyto1D(int x,int y){
        return (n*x+y);
    }
    public static void open(int i,int j){
        A[i][j]=1;
        if(A[i-1][j]==1) {WQUF.union(xyto1D(i-1,j),xyto1D(i,j))};
        if(A[i+1][j]==1) {WQUF.union(xyto1D(i+1,j),xyto1D(i,j))};
        if(A[i][j-1]==1) {WQUF.union(xyto1D(i,j-1),xyto1D(i,j))};
        if(A[i][j+1]==1) {WQUF.union(xyto1D(i,j+1),xyto1D(i,j))};
    }
    public static boolean isOpen(int x,int y){
        return (A[x][y]==1);
    }
    public static boolean isFull(int x,int y){
        return (WQUF.connected(xyto1D(x,y),0));
    }
    public static boolean percolates(){
        for (i=n*n-n+1;i<=n*n;i++)
        {
            if ((isFull(i))&&(isOpen(i))) return TRUE;
        }
        return FALSE;
    }
}

我在编译过程中遇到以下错误：

35 errors found:
File: C:UsersAdministratoralgs4Percolation.java  
[line: 7]
Error: illegal start of type
File: C:UsersAdministratoralgs4Percolation.java  
[line: 7]
Error: <identifier> expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 7]
Error: ';' expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 7]
Error: <identifier> expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 7]
Error: <identifier> expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 7]
Error: <identifier> expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 7]
Error: illegal start of type
File: C:UsersAdministratoralgs4Percolation.java  
[line: 7]
Error: <identifier> expected
File: C:UsersAdministratoralgs4Percolati
on.java  
[line: 8]
Error: ';' expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 9]
Error: illegal start of type
File: C:UsersAdministratoralgs4Percolation.java  
[line: 9]
Error: illegal start of type
File: C:UsersAdministratoralgs4Percolation.java  
[line: 9]
Error: <identifier> expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 11]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 11]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 11]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 14]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 17]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 18]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 20]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 22]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 23]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 25]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 26]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 27]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 28]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 29]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 30]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 32]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 33]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 35]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 36]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 37]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 37]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 40]
Error: class, interface, or enum expected
File: C:UsersAdministratoralgs4Percolation.java  
[line: 42]
Error: class, interface, or enum expected

Answer 1

关闭第四行中的构造函数，每个错误都是由此产生的。

    public static Percolation(int n){
        boolean[][] A=new boolean[n][n];
    } // <<--- here

请处理你的压痕。如果我没记错的话，eclipse和netbeans都有某种自动缩进。如果有适当的压痕，你会很容易地自己抓住它的。

Answer 2

还有一个问题：（除了许多其他语法错误外，您还可以逐行调试，这样您就可以知道在哪里以及所有违反Java语法规则的内容）

WeightedQuickUnionUF WQUF=new WeightedQuickUnionUF[n*n+2];

您应该将其更改为：

WeightedQuickUnionUF WQUF=new WeightedQuickUnionUF(n*n+2);

Answer 3

 do {
i=StdRandom.uniform(n-1)+1;
j=StdRandom.uniform(n-1)+1;
} while(A[i][j]!=0)

您需要将分号放在while语句的末尾。

do {
i=StdRandom.uniform(n-1)+1;
j=StdRandom.uniform(n-1)+1;
} while(A[i][j]!=0);

代码似乎有很多问题。我建议您使用Eclipse IDE。

Answer 4

在Java中，每个可执行代码（初始化除外）都需要放在一个块（静态或函数）中。

然而，在文件的第7行，类的主体中有一个for循环，这是无效的。请将它放在构造函数或其他函数中。

事实上，您发布的代码还有一个问题。您已声明构造函数为static，这是不允许的。构造函数不能是静态的。

public static Percolation(int n) {  // illegal
boolean[][] A = new boolean[n][n];
}

假设从第7行开始的代码是构造函数的一部分，下面是应该工作于的代码

public class Percolation {
    public Percolation(int n) {
    boolean[][] A = new boolean[n][n];
        int i, j;
        WeightedQuickUnionUF WQUF = new WeightedQuickUnionUF[n * n + 2];

        for(i=1;i<=n;i++){
           WQUF.union(0,i);
        }
        for (i=n*n-n+1;i<=n*n;i++){
            WQUF.union(n*n+1,i);
        }
        do{
            i=StdRandom.uniform(n-1)+1;
            j=StdRandom.uniform(n-1)+1;
        } while(A[i][j]!=0); //add this semicolon as well.
        open(i,j);
    }
    private static int xyto1D(int x, int y) {
    return (n * x + y);
    }
    public static void open(int i,int j){
        A[i][j]=1;
        if(A[i-1][j]==1) {WQUF.union(xyto1D(i-1,j),xyto1D(i,j))};
         if(A[i+1][j]==1) {WQUF.union(xyto1D(i+1,j),xyto1D(i,j))};
          if(A[i][j-1]==1) {WQUF.union(xyto1D(i,j-1),xyto1D(i,j))};
           if(A[i][j+1]==1) {WQUF.union(xyto1D(i,j+1),xyto1D(i,j))};
    }
    public static boolean isOpen(int x, int y) {
    return (A[x][y] == 1);
    }
    public static boolean isFull(int x, int y) {
    return (WQUF.connected(xyto1D(x, y), 0));
    }
    public static boolean percolates() {
    for (i = n * n - n + 1; i <= n * n; i++) {
        if ((isFull(i)) && (isOpen(i)))
        return TRUE;
    }
    return FALSE;
    }
}