更新的JDK已经实现了AbstractCollection.toString()，并且Stack扩展了AbstractCollection，所以你只需要在你的集合上调用toString():

    public abstract class AbstractCollection<E> implements Collection<E> {
    ...
    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(',').append(' ');
        }
    }

对于Apache Commons 3，您希望调用

StringUtils.join(myCollection, ",")

JSON

另一种解决方案是将您的集合转换为JSON格式并打印JSON - string。其优点是格式良好且可读的Object-String，而不需要实现toString()。

使用谷歌的Gson的示例:

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

...

    printJsonString(stack);

...
public static void printJsonString(Object o) {
    GsonBuilder gsonBuilder = new GsonBuilder();
    /*
     * Some options for GsonBuilder like setting dateformat or pretty printing
     */
    Gson gson = gsonBuilder.create();
    String json= gson.toJson(o);
    System.out.println(json);
}

我同意上面关于在您自己的类上重写toString()的评论(以及关于尽可能自动化该过程)。

对于你没有定义的类，你可以为你想要处理的每个库类编写一个重载方法的ToStringHelper类:

public class ToStringHelper {
    //... instance configuration here (e.g. punctuation, etc.)
    public toString(List m) {
        // presentation of List content to your liking
    }
    public toString(Map m) {
        // presentation of Map content to your liking
    }
    public toString(Set m) {
        // presentation of Set content to your liking
    }
    //... etc.
}

编辑:针对xukxpvfzflbbld的评论，下面是针对前面提到的情况的可能实现。

package com.so.demos;

import java.util.List;
import java.util.Map;
import java.util.Set;

public class ToStringHelper {

    private String separator;
    private String arrow;

    public ToStringHelper(String separator, String arrow) {
        this.separator = separator;
        this.arrow = arrow;
    }

   public String toString(List<?> l) {
        StringBuilder sb = new StringBuilder("(");
        String sep = "";
        for (Object object : l) {
            sb.append(sep).append(object.toString());
            sep = separator;
        }
        return sb.append(")").toString();
    }

    public String toString(Map<?,?> m) {
        StringBuilder sb = new StringBuilder("[");
        String sep = "";
        for (Object object : m.keySet()) {
            sb.append(sep)
              .append(object.toString())
              .append(arrow)
              .append(m.get(object).toString());
            sep = separator;
        }
        return sb.append("]").toString();
    }

    public String toString(Set<?> s) {
        StringBuilder sb = new StringBuilder("{");
        String sep = "";
        for (Object object : s) {
            sb.append(sep).append(object.toString());
            sep = separator;
        }
        return sb.append("}").toString();
    }

}

这不是一个成熟的实现，而只是一个开始。

应该适用于Map之外的任何集合，但也很容易支持。 如果需要，修改代码以将这3个字符作为参数传递。

static <T> String seqToString(Iterable<T> items) {
    StringBuilder sb = new StringBuilder();
    sb.append('[');
    boolean needSeparator = false;
    for (T x : items) {
        if (needSeparator)
            sb.append(' ');
        sb.append(x.toString());
        needSeparator = true;
    }
    sb.append(']');
    return sb.toString();
}

只是修改了前面的示例，以打印包含用户自定义对象的偶数集合。

public class ToStringHelper {

    private  static String separator = "\n";

    public ToStringHelper(String seperator) {
        super();
        ToStringHelper.separator = seperator;

    }

    public  static String toString(List<?> l) {
        StringBuilder sb = new StringBuilder();
        String sep = "";
        for (Object object : l) {
            String v = ToStringBuilder.reflectionToString(object);
            int start = v.indexOf("[");
            int end = v.indexOf("]");
            String st =  v.substring(start,end+1);
            sb.append(sep).append(st);
            sep = separator;
        }
        return sb.toString();
    }

    public static String toString(Map<?,?> m) {
        StringBuilder sb = new StringBuilder();
        String sep = "";
        for (Object object : m.keySet()) {
            String v = ToStringBuilder.reflectionToString(m.get(object));
            int start = v.indexOf("[");
            int end = v.indexOf("]");
            String st =  v.substring(start,end+1);
            sb.append(sep).append(st);
            sep = separator;
        }
        return sb.toString();
    }

    public static String toString(Set<?> s) {
        StringBuilder sb = new StringBuilder();
        String sep = "";
        for (Object object : s) {
            String v = ToStringBuilder.reflectionToString(object);
            int start = v.indexOf("[");
            int end = v.indexOf("]");
            String st =  v.substring(start,end+1);
            sb.append(sep).append(st);
            sep = separator;
        }
        return sb.toString();
    }

    public static void print(List<?> l) {
        System.out.println(toString(l));    
    }
    public static void print(Map<?,?> m) {
        System.out.println(toString(m));    
    }
    public static void print(Set<?> s) {
        System.out.println(toString(s));    
    }

}