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[英]Java - Passing a parameter to a class constructor, when an array of that class is being created
[英]Passing a Collection<user defined class> as a parameter to the constructor of the class in java
在下面的代碼片段中,如何使用coll
訪問類B中的變量? 我想在A.main()
方法的coll
中添加數據,並使用循環打印所有數據。
class A{
class B{
String str;
int i1;
int i2;
}
private Collection<B> coll;
public A(Collection<B> _coll){
coll = _coll;
}
}
您想要在main()
中做什么,是這樣嗎?
Collection<A.B> newColl = Arrays.asList(new A.B("Lion", 114, 1), new A.B("Java", 9, -1));
A myAInstance = new A(newColl);
myAInstance.printAll();
如果我猜對了,下面的代碼可以做到。 如果沒有,請編輯您的問題並解釋。
public class A {
public static class B {
String str;
int i1;
int i2;
public B(String str, int i1, int i2) {
this.str = str;
this.i1 = i1;
this.i2 = i2;
}
@Override
public String toString() {
return String.format("%-10s%4d%4d", str, i1, i2);
}
}
private Collection<B> coll;
// in most cases avoid underscore in names, especailly names in the public interface of a class
public A(Collection<B> coll) {
this.coll = coll;
// or may make a "defensive copy" so that later changes to the collection passed in doesn’t affect this instance
// this.coll = new ArrayList<>(coll);
}
public void printAll() {
// Requirements said "print all data using a loop", so do that
for (B bInstance : coll) {
System.out.println(bInstance);
// may also access variables from B, for instance like:
// System.out.println(bInstance.str + ' ' + bInstance.i1 + ' ' + bInstance.i2);
}
}
}
現在,我為main()
建議的代碼將打印:
Lion 114 1
Java 9 -1
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