join data structure to a string - Java java.lang

Java examples for java.lang:String Join

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Introduction

The following code shows how to join

Demo Code

//package com.java2s;

import java.util.Collection;
import java.util.Iterator;

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

    public static String join(Object[] array) {
        return join(array, null);
    }/*from www.  j  av a2  s .  c om*/

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

        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 bufSize = (endIndex - startIndex);
        if (bufSize <= 0) {
            return EMPTY;
        }

        bufSize *= ((array[startIndex] == null ? 16 : array[startIndex]
                .toString().length()) + 1);
        StringBuilder buf = new StringBuilder(bufSize);

        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 bufSize = (endIndex - startIndex);
        if (bufSize <= 0) {
            return EMPTY;
        }

        bufSize *= ((array[startIndex] == null ? 16 : array[startIndex]
                .toString().length()) + separator.length());

        StringBuilder buf = new StringBuilder(bufSize);

        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(Collection collection, char separator) {
        if (collection == null) {
            return null;
        }
        return join(collection.iterator(), separator);
    }

    public static String join(Collection collection, String separator) {
        if (collection == null) {
            return null;
        }
        return join(collection.iterator(), separator);
    }

    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 first.toString();
        }

        // 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 first.toString();
        }

        // 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();
    }
}

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