Java Collection Max valueOfCollection(Collection c, int maxLength)

Description

This returns a String representation of a Collection, with a maximum length specified.

License

Open Source License

Declaration

public static String valueOfCollection(Collection<?> c, int maxLength) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.util.*;

public class Main {
    /** This returns a String representation of a Collection, with a maximum length specified. This is useful in getting a string representation of a potentially very large collection object without running out of memory.
     * It protects against large numbers of elements in collections, but cannot protect against very large single elements in collections whose toString() method exceeds available memory. */
    public static String valueOfCollection(Collection<?> c, int maxLength) {
        if (c == null)
            return "";

        Iterator<?> i = c.iterator();
        if (!i.hasNext())
            return "[]";

        StringBuilder sb = new StringBuilder((int) (maxLength * 1.5));
        sb.append('[');
        for (;;) {
            Object e = i.next();/*w w w .ja  v  a  2  s . co  m*/
            String s;
            if (e == c) {
                s = "(this Collection)";
            } else {
                s = String.valueOf(e);
                if (s.length() > maxLength) {
                    s = s.substring(0, maxLength - 1);
                }
            }
            sb.append(s);
            if (sb.length() >= maxLength) {
                if (sb.length() > maxLength) {
                    sb.delete(1000, sb.length() - 1);
                }
                return sb.append("<truncated...>").toString();
            } else if (!i.hasNext()) {
                return sb.append(']').toString();
            }
            sb.append(", ");
        }
    }

    /** This works the same as {@link String#valueOf(Object)}, except it returns an empty string instead of "null" if the input is null. */
    public static String valueOf(Object o) {
        return o == null ? "" : String.valueOf(o);
    }
}

Related

1. partitionFixed(int maxNumChunks, Collection coll)
2. toString(Collection collection, int maxLen)
3. toString(Collection entries, int max)
4. transfer(Collection source, Collection dest, int maxElems)
5. truncate(Collection coll, int maximumSize)