假设我有以下试图不可变的类
public class Computation {
private final Operation operation;
private final double epsilon;
public Computation(Operation operation) {
this.operation = operation;
//Default value
epsilon = 0.01;
}
public Computation(Operation operation double epsilon) {
this(operation);
//Won't compile as epsilon is final and is set by the other constructor
this.epsilon = epsilon;
}
}
而且,为了这个问题,让我们假设我不想为这个类使用构建器(这将解决问题)。
所以问题是:
有没有办法在不删除 epsilon 的 final 修饰符并保留两个构造函数的情况下实现这种行为?
也就是说,没有做类似的事情
public class Computation {
private final Operation operation;
private final double epsilon;
public Computation(Operation operation Double epsilon) {
this(operation);
this.epsilon = (epsilon == null) ? 0.01 : epsilon;
}
}
并且不使用构建器
public class Computation {
private final Operation operation;
private final double epsilon;
private Computation(Builder builder) {
this.operation = builder.operation;
this.epsilon = builder.epsilon;
}
public static class Builder {
private final Operation operation;
//Default value
private double epsilon = 0.01;
public Builder(Operation operation) {
this.operation = operation;
}
public Builder epsilon(double epsilon) {
this.epsilon = epsilon;
return this;
}
public Computation build() {
return new Computation(this);
}
}