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Question

我有一个由Land扩展的SimpleBoard类，然后由Units扩展。每当我尝试编译单位时，我都会收到此错误：

cannot find symbol
symbol  : constructor Land()
location: class Land
    public Units(int x, int y){

关于什么是错的想法？

编辑：对不起，我赶时间！这是完整的代码：

public class Units extends Land{

    private int attack;

    public Units(int x, int y) {

        if(x==1){
            attack = 1;
        }
        else if(x==2)
            attack = 2;
        else if(x==3)
            attack = 4;
        ar[y].AddUnit(this);
    }

    public int getAttack(){
        return attack;
    }
    }

和土地

public class Land extends SimpleBoard {
    private boolean barrel = false;
    private boolean crown = false;
    private boolean castle = false;
    private boolean stronghold = false;
    private int num;
    private int array = 0;
    public int[] adjacent;
    private Units [] Occupy = new Units [4];

    public Land(int z, int x, int c, int v, int b, int[] array){
        if(z == 1)
            barrel = true;
        if(x == 1)
            crown = true;
        if(c == 1)
            castle = true;
        if (v==1)
            stronghold = true;
        num = b;
        adjacent = array;
    }

    public void addUnit(Units x){
        Occupy[array] = x;
        array++;
    }

    public boolean checkB(){
        return barrel;
    }


    public int getAdj(int i){
        return adjacent[i];
    }
    }

并登上

public class SimpleBoard {
    public static Land[] ar = new Land[3];
    public static void main(String[] args){
    Land One = new Land(1,0,0,0,1, new int[]{2, 3});
    Land Two = new Land(0,1,0,0,2, new int[]{1, 3});
    Land Three = new Land(0,0,1,0,3, new int[]{1, 2});
    ar[0] = One;
    ar[1] = Two;
    ar[2] = Three;

    Units Footman = new Units(1, 1);
    Units Knight = new Units(2, 3);
    Units Siege = new Units(3, 2);

    }
    }

Answer 1

您可以将Units和Land课程更改为此课程：

public class Units extends Land {

    private int attack;

    public Units(int z, int x, int c, int v, int b, int[] array) {
        super(z, x, c, v, b, array);
    }

    public Units(int x, int y) {

        if (x == 1) {
            attack = 1;
        } else if (x == 2) {
            attack = 2;
        } else if (x == 3) {
            attack = 4;
        }
        ar[y].addUnit(this);
    }

    public int getAttack() {
        return attack;
    }
}

public class Land extends SimpleBoard {

    // Declared variable

    public Land(int x, int y) {

    }

    // Rest of the code...
}

由于继承，您在Units类中声明的构造函数也必须存在于Land类中。

在名为Land的{{1}}类中添加一个构造函数，其中没有任何代码（只是一个空白构造函数），这样它就会删除Land(int x, int y)类中的错误。这不是最好的做法，因为我不知道你想做什么。如果你赶时间，你可以尝试这个，但如果你有时间，请简要说明你的申请目的。

更新

<强> SimpleBoardGame.java

Units

<强> Land.java

public class SimpleBoardGame {

    private static Land[] ar = new Land[3];

    public static Land[] getAr() {
        return ar;
    }

    public static void main(String[] args) {
        Land One = new Land(1, 0, 0, 0, 1, new int[]{2, 3});
        Land Two = new Land(0, 1, 0, 0, 2, new int[]{1, 3});
        Land Three = new Land(0, 0, 1, 0, 3, new int[]{1, 2});
        ar[0] = One;
        ar[1] = Two;
        ar[2] = Three;

        // When you pass the parameter for 'y' please make sure it already minus by one.
        // If not, will occur the 'java.lang.ArrayIndexOutOfBoundsException'
        Unit Footman = new Unit(1, 0);
        Unit Knight = new Unit(2, 2);
        Unit Siege = new Unit(3, 1);

    }
}

Unit.java （从public class Land { // For boolean variable, no need to set the value as "false" since it default is "false". private boolean barrel; private boolean crown; private boolean castle; private boolean stronghold; private int num; private int array = 0; public int[] adjacent; private Unit[] Occupy = new Unit[4]; public Land(int x, int y) { // Empty constructor... } public Land(int z, int x, int c, int v, int b, int[] array) { if (z == 1) { barrel = true; } if (x == 1) { crown = true; } if (c == 1) { castle = true; } if (v == 1) { stronghold = true; } num = b; adjacent = array; } public void addUnit(Unit x) { Occupy[array] = x; array++; } public boolean checkB() { return barrel; } public int getAdj(int i) { return adjacent[i]; } }更改为Units.java）

Unit.java

注意：请确保不继承public class Unit extends Land { private int attack; public Unit(int z, int x, int c, int v, int b, int[] array) { super(z, x, c, v, b, array); } public Unit(int x, int y) { super(x, y); if (x == 1) { attack = 1; } else if (x == 2) { attack = 2; } else if (x == 3) { attack = 4; } addUnit(y); } /** * Overload method of the addUnit() of Land class. * Better not use "this" inside the constructor. * * @param y */ public final void addUnit(int y) { SimpleBoardGame.getAr()[y].addUnit(this); } public int getAttack() { return attack; } }作为SimpleBoardGame类中的主类，如果要访问主类中的变量，只需创建setter和getter为了那个原因。您可以像Land这样访问SimpleBoardGame.getAr()[y].addUnit(this);（请参阅addUnit(int y)类中的方法Unit。

Answer 2

这个想法很简单：

Child继承自Parent。在Child构造函数中，您需要首先通过调用Parent的构造函数来构造对象的“Parent”部分，然后构造子部件。

由超级（...）语句完成：

class Animal {
    String name;

    public Animal(String name) {
        this.name = name;
    }
}

class Human extends Animal {
    String familyName;

    public Human(String name, String familyName) {
        super(name);    // HERE!!!! means calling Animal's Animal(String) ctor
        this.familyName = familyName;
    }
}

如果您没有显式添加super（...）语句，编译器将假定您正在调用Parent类的无参数构造函数。

对于没有定义构造函数的类，编译器将为它添加一个默认的无参数构造函数。但是，由于您的Land具有已定义的公共Land（int z，int x，int c，int v，int b，int [] array）构造函数，这意味着您将不会在Land中具有无参数构造函数。

在Unit的构造函数中，没有super（...）语句，这意味着它将尝试调用Land的无参数构造函数（它不存在），这会导致问题

编辑：虽然有点偏离主题，但在我看来，你对继承的使用没有任何意义。为什么“Land”是一个“SimpleBoard”？为什么“单位”是“土地”？他们似乎是一个“有一个”的关系而不是“是一个”给我。考虑重新设计您的应用程序，否则您将面临更多奇怪的问题

java在第二类中找不到构造函数

2 个答案:

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