英文:
How to convert Array Of Object A to Array Of Object B with Constructor of A Using Java 8?
问题
我有两个类，Class A 和 Class B。如下所示：
Class A:
class A {
public String a;
public A() {
}
public A(final String a) {
this.a = a;
}
}
Class B:
class B {
private A a;
private String b;
public B() {
}
public B(final A a) {
this.a = a;
}
}
我正在将 A[] 转换为 B[]，如下所示：
public static void main(final String[] args) {
final A[] myA = new A[3];
myA[0] = new A("a");
myA[1] = new A("b");
myA[2] = new A("c");
B[] myB = new B[myA.length];
IntStream.range(0, myA.length).forEach(propIndex->{
myB[propIndex] = new B(myA[propIndex]);
});
System.out.println(myB.length);
}
是否有其他方法可以在不使用索引的情况下完成，类似于toArray(B[]::new)或者其他不需要使用forEach的方式？
英文:
I have two Classes Class A and Class B. As below:
Class A:
class A {
public String a;
public A() {
}
public A(final String a) {
this.a = a;
}
}
Class B:
class B {
private A a;
private String b;
public B() {
}
public B(final A a) {
this.a = a;
}
}
Where I am converting A[] to B[] as below:
public static void main(final String[] args) {
final A[] myA = new A[3];
myA[0] = new A("a");
myA[1] = new A("b");
myA[2] = new A("c");
B[] myB = new B[myA.length];
IntStream.range(0, myA.length).forEach(propIndex->{
myB[propIndex] = new B(myA[propIndex]);
});
System.out.println(myB.length);
}
Is there any other way to do it without iterating(forEach) with Index? Something with toArray(B[]::new) or any other way where I don't have to use forEach?
答案1
得分: 8
可以这样做：
B[] myB = Arrays.stream(myA) // 创建一个 Stream<A>
.map(B::new) // 将每个 A 的实例映射为 B 的实例
.toArray(B[]::new); // 收集到 B 的数组
英文:
You can do:
B[] myB = Arrays.stream(myA) // create a Stream<A>
.map(B::new) // map each instance of A to instance of B
.toArray(B[]::new); // collect to array of B
答案2
得分: 2
IntStream虽然不是最差的选择，但使用常规循环进行迭代传输可能会更快（尽管有人可能会认为可读性较差）。
B[] myB = new B[myA.length];
for (int i = 0; i < myA.length; ++i) {
myB[i] = new B(myA[i]);
}
英文:
IntStream is not the worst, though an iterative transfer with a regular loop would probably be faster here (though arguably less readable).
B[] myB = new B[myA.length];
for (int i = 0; i < myA.length; ++i) {
myB[i] = new B(myA[i]);
}
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