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[英]Constructor call must be the first statement in a constructor in super()
[英]error: Super must be first statement in constructor
無法弄清楚為什么我收到此錯誤。 在記事本中工作,通過cmd運行Javac(顯然對文件而言更多)。 如果您需要我鏈接更多,我可以。 我的錯誤發生在“ setCruiseShip”,我試圖將當前鏈接鏈接到超類。 錯誤:對super的調用必須是構造函數中的第一條語句。
class Ship
{ protected String name;
protected float speed;
protected int year;
public Ship() {name=""; speed=year=0;}
public Ship(String n, float sp, int y) {name=n; speed=sp; year=y;}
public String getName() {return name;}
public float getSpeed() {return speed;}
public int getYear() {return year;}
public void setShip(String n, float sp, int y) {name=n; speed=sp; year=y;}
public String toString() {return "Ship named "+name+ " with max speed of "
+speed+ " was built in " +year;}
}
class CruiseShip extends Ship
{ protected int maxpass;
public CruiseShip() {super(); maxpass=0;}
public CruiseShip(String n, float sp, int y, int mp) {super(n, sp, y);
maxpass=mp;}
public int setMaxpass(int mp) {maxpass=mp;}
public void setCruiseShip(String n, float sp, int y, int mp){super(n,sp,y);
maxxpass=mp;}
public String toString() { return super.toString() +" carries "
+maxpass+ " passengers";}
}
class Ship
沒有名為setCruiseShip
方法。 您可能想要的是調用setShip
方法。 更換
super(n,sp,y);
與
setShip(n,sp,y);
超級構造函數只能從子類的構造函數調用(不能從任何方法調用)。 下面給出了經過修改和編譯的程序
class Ship {
protected String name;
protected float speed;
protected int year;
public Ship() {
name = "";
speed = year = 0;
}
public Ship(String n, float sp, int y) {
name = n;
speed = sp;
year = y;
}
public String getName() {
return name;
}
public float getSpeed() {
return speed;
}
public int getYear() {
return year;
}
public void setShip(String n, float sp, int y) {
name = n;
speed = sp;
year = y;
}
public String toString() {
return "Ship named " + name + " with max speed of " + speed
+ " was built in " + year;
}
}
class CruiseShip extends Ship {
protected int maxpass;
public CruiseShip() {
super();
maxpass = 0;
}
public CruiseShip(String n, float sp, int y, int mp) {
super(n, sp, y);
maxpass = mp;
}
public int setMaxpass(int mp) {
maxpass = mp;
}
public void setCruiseShip(String n, float sp, int y, int mp) {
setShip(n, sp, y);
maxpass = mp;
}
public String toString() {
return super.toString() + " carries " + maxpass + " passengers";
}
}
可以從子類的構造函數中調用super(somevalues...)
。 Java不允許從方法中調用super(somevalues...)
。 同樣,當您在子類中定義構造函數時,其第一條語句應該是super()/super(somevalues)
構造函數或this(somevalues...)
。 如果不這樣做,則編譯器會隱式添加默認的no-arg超級構造函數。
this()
表示構造函數重載。
給定的事實是
public void setCruiseShip(String n, float sp, int y, int mp){super(n,sp,y);
不是子類的構造函數。
構造函數definition
是,構造函數名稱必須與沒有返回類型的類名稱相同(我不是說“應該”),並且允許使用任何訪問修飾符(例如private,default,protected,public)。
所以setCruiseShip
與CruiseShip
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