Java Collection 在小括号中打印值并用空格分隔？

Question

如何创建一个通用的 java 集合来打印如下值:(带小括号且不带逗号)

SomeGenericCollection someGenericCollectionInstance = new SomeGenericColllection();

someGenericCollectionInstance.add("A");
someGenericCollectionInstance.add("B");

System.out.println(someGenericCollectionInstance);

预期输出是:

(“A”“B”)

其他场景:

SomeGenericCollection someGenericCollectionInstance = new SomeGenericColllection();

someGenericCollectionInstance.add(1);
someGenericCollectionInstance.add(2);

System.out.println(someGenericCollectionInstance);

(1 2)

Answer 1

如果我理解正确的话，您只想重写 AbstractCollection 的 toString 方法。像这样:

public abstract class MyCollection<E> extends AbstractCollection<E> {

@Override
public String toString() {
    Iterator<E> it = iterator();
    if (! it.hasNext())
        return "()";

    StringBuilder sb = new StringBuilder();
    sb.append('(');
    for (;;) {
        E e = it.next();
        sb.append(e == this ? "(this Collection)" : e);
        if (! it.hasNext())
            return sb.append(')').toString();
        sb.append(' ');
    }
}

}