Java Array Join join(Object[] array, char separator)

Description

join

License

Apache License

Declaration

public static String join(Object[] array, char separator) 

Method Source Code

//package com.java2s;
//License from project: Apache License 

import java.util.Iterator;

public class Main {
    private static final String EMPTY = "";

    public static String join(Object[] array, char separator) {
        if (array == null) {
            return null;
        }/*  w  w w .jav  a 2 s.  c o m*/

        return join(array, separator, 0, array.length);
    }

    public static String join(Object[] array, char separator, int startIndex, int endIndex) {
        if (array == null) {
            return null;
        }
        int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }

        StringBuilder buf = new StringBuilder(noOfItems * 16);

        for (int i = startIndex; i < endIndex; i++) {
            if (i > startIndex) {
                buf.append(separator);
            }
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
    }

    public static String join(Object[] array, String separator) {
        if (array == null) {
            return null;
        }
        return join(array, separator, 0, array.length);
    }

    public static String join(Object[] array, String separator, int startIndex, int endIndex) {
        if (array == null) {
            return null;
        }
        if (separator == null) {
            separator = EMPTY;
        }

        // endIndex - startIndex > 0:   Len = NofStrings *(len(firstString) + len(separator))
        //           (Assuming that all Strings are roughly equally long)
        int noOfItems = endIndex - startIndex;
        if (noOfItems <= 0) {
            return EMPTY;
        }

        StringBuilder buf = new StringBuilder(noOfItems * 16);

        for (int i = startIndex; i < endIndex; i++) {
            if (i > startIndex) {
                buf.append(separator);
            }
            if (array[i] != null) {
                buf.append(array[i]);
            }
        }
        return buf.toString();
    }

    public static String join(Iterator<?> iterator, char separator) {

        // handle null, zero and one elements before building a buffer
        if (iterator == null) {
            return null;
        }
        if (!iterator.hasNext()) {
            return EMPTY;
        }
        Object first = iterator.next();
        if (!iterator.hasNext()) {
            return toString(first);
        }

        // two or more elements
        StringBuilder buf = new StringBuilder(256); // Java default is 16, probably too small
        if (first != null) {
            buf.append(first);
        }

        while (iterator.hasNext()) {
            buf.append(separator);
            Object obj = iterator.next();
            if (obj != null) {
                buf.append(obj);
            }
        }

        return buf.toString();
    }

    public static String join(Iterator<?> iterator, String separator) {

        // handle null, zero and one elements before building a buffer
        if (iterator == null) {
            return null;
        }
        if (!iterator.hasNext()) {
            return EMPTY;
        }
        Object first = iterator.next();
        if (!iterator.hasNext()) {
            return toString(first);
        }

        // two or more elements
        StringBuilder buf = new StringBuilder(256); // Java default is 16, probably too small
        if (first != null) {
            buf.append(first);
        }

        while (iterator.hasNext()) {
            if (separator != null) {
                buf.append(separator);
            }
            Object obj = iterator.next();
            if (obj != null) {
                buf.append(obj);
            }
        }
        return buf.toString();
    }

    public static String join(Iterable<?> iterable, char separator) {
        if (iterable == null) {
            return null;
        }
        return join(iterable.iterator(), separator);
    }

    public static String join(Iterable<?> iterable, String separator) {
        if (iterable == null) {
            return null;
        }
        return join(iterable.iterator(), separator);
    }

    public static String toString(Object obj) {
        return obj == null ? "" : obj.toString();
    }

    public static String toString(Object obj, String nullStr) {
        return obj == null ? nullStr : obj.toString();
    }
}

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