假设我有以下类试图保持不变
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)。
那么问题是:
有没有办法在不删除 epsilon 的最终修饰符并保留两个构造函数的情况下实现此行为?
也就是说,不做类似的事情
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);
}
}
最佳答案
是的 - 颠倒逻辑,以便您的构造函数使用更少参数调用具有更多的构造函数:
public Computation(Operation operation) {
this(operation, 0.01);
}
public Computation(Operation operation, double epsilon) {
this.operation = operation;
this.epsilon = epsilon;
}
基本上这样你可以得到很多构造函数,它们都只委托(delegate)给一个“真正的”构造函数来完成所有实际工作。
关于java - 重用具有最终实例字段的构造函数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/2325498/