阿里巴巴机试题，根据注释里的方法调用的结果，写全方法的实现代码，一共四个方法
public class StringUtils {
/**
* StringUtils.join(null, *) = null
* StringUtils.join([], *) = ""
* StringUtils.join([null], *) = ""
* StringUtils.join(["a", "b", "c"], ';') = "a;b;c"
* StringUtils.join(["a", "b", "c"], null) = "abc"
* StringUtils.join([null, "", "a"], ';') = ";;a"
*/
public static String join(Object[] array, char separator) {
return null;
}
/**
* <p>Left pad a String with a specified character.</p>
*
* <p>Pad to a size of {@code size}.</p>
*
* <pre>
* StringUtils.leftPad(null, *, *) = null
* StringUtils.leftPad("", 3, 'z') = "zzz"
* StringUtils.leftPad("bat", 3, 'z') = "bat"
* StringUtils.leftPad("bat", 5, 'z') = "zzbat"
* StringUtils.leftPad("bat", 1, 'z') = "bat"
* StringUtils.leftPad("bat", -1, 'z') = "bat"
* </pre>
*
* @param str the String to pad out, may be null
* @param size the size to pad to
* @param padChar the character to pad with
* @return left padded String or original String if no padding is necessary,
* {@code null} if null String input
* @since 2.0
*/
public static String leftPad(String str, int size, String padChar) {
return null;
}
/**
* <p>Right pad a String with a specified character.</p>
*
* <p>The String is padded to the size of {@code size}.</p>
*
* <pre>
* StringUtils.rightPad(null, *, *) = null
* StringUtils.rightPad("", 3, 'z') = "zzz"
* StringUtils.rightPad("bat", 3, 'z') = "bat"
* StringUtils.rightPad("bat", 5, 'z') = "batzz"
* StringUtils.rightPad("bat", 1, 'z') = "bat"
* StringUtils.rightPad("bat", -1, 'z') = "bat"
* </pre>
*
* @param str the String to pad out, may be null
* @param size the size to pad to
* @param padChar the character to pad with
* @return right padded String or original String if no padding is necessary,
* {@code null} if null String input
* @since 2.0
*/
public static String rightPad(String str, int size, String padChar) {
return null;
}
/**
* <p>Capitalizes a String changing the first letter to title case as
* per {@link Character#toTitleCase(char)}. No other letters are changed.</p>
*
* <pre>
* StringUtils.capitalize(null) = null
* StringUtils.capitalize("") = ""
* StringUtils.capitalize("cat") = "Cat"
* StringUtils.capitalize("cAt") = "CAt"
* </pre>
*
* @param str the String to capitalize, may be null
* @return the capitalized String, {@code null} if null String input
* @since 2.0
*/
public static String capitalize(String str) {
return null;
}
public static void main(String[] args) {
}
}
public class StringUtils {
/**
* StringUtils.join(null, *) = null
* StringUtils.join([], *) = ""
* StringUtils.join([null], *) = ""
* StringUtils.join(["a", "b", "c"], ';') = "a;b;c"
* StringUtils.join(["a", "b", "c"], null) = "abc"
* StringUtils.join([null, "", "a"], ';') = ";;a"
*/
// FIXME 这里面第二个参数如果是char，根本传不进去null，所以改成Character
public static String join(Object[] array, Character separator) {
if(null != array) {
if(array.length==0) return "";
StringBuilder sb = new StringBuilder();
boolean hasSep = false;
for (Object a : array) {
if (null != a) {
sb.append(a);
}
if (null != separator) {
hasSep = true;
sb.append(separator);
}
}
if(hasSep) {
return sb.substring(0, sb.length() - 1);
} else{
return sb.toString();
}
}
return null;
}
/**
* <p>Left pad a String with a specified character.</p>
*
* <p>Pad to a size of {@code size}.</p>
*
* <pre>
* StringUtils.leftPad(null, *, *) = null
* StringUtils.leftPad("", 3, 'z') = "zzz"
* StringUtils.leftPad("bat", 3, 'z') = "bat"
* StringUtils.leftPad("bat", 5, 'z') = "zzbat"
* StringUtils.leftPad("bat", 1, 'z') = "bat"
* StringUtils.leftPad("bat", -1, 'z') = "bat"
* </pre>
*
* @param str the String to pad out, may be null
* @param size the size to pad to
* @param padChar the character to pad with
* @return left padded String or original String if no padding is necessary,
* {@code null} if null String input
* @since 2.0
*/
public static String leftPad(String str, int size, String padChar) {
if(null == str) return null;
if(str.length()>=size) return str;
else{
StringBuilder sb = new StringBuilder();
for(int i=0;i<size-str.length();i++){
sb.append(padChar);
}
sb.append(str);
return sb.toString();
}
}
/**
* <p>Right pad a String with a specified character.</p>
*
* <p>The String is padded to the size of {@code size}.</p>
*
* <pre>
* StringUtils.rightPad(null, *, *) = null
* StringUtils.rightPad("", 3, 'z') = "zzz"
* StringUtils.rightPad("bat", 3, 'z') = "bat"
* StringUtils.rightPad("bat", 5, 'z') = "batzz"
* StringUtils.rightPad("bat", 1, 'z') = "bat"
* StringUtils.rightPad("bat", -1, 'z') = "bat"
* </pre>
*
* @param str the String to pad out, may be null
* @param size the size to pad to
* @param padChar the character to pad with
* @return right padded String or original String if no padding is necessary,
* {@code null} if null String input
* @since 2.0
*/
public static String rightPad(String str, int size, String padChar) {
if(null == str) return null;
if(str.length()>=size) return str;
else{
StringBuilder sb = new StringBuilder();
sb.append(str);
for(int i=0;i<size-str.length();i++){
sb.append(padChar);
}
return sb.toString();
}
}
/**
* <p>Capitalizes a String changing the first letter to title case as
* per {@link Character#toTitleCase(char)}. No other letters are changed.</p>
*
* <pre>
* StringUtils.capitalize(null) = null
* StringUtils.capitalize("") = ""
* StringUtils.capitalize("cat") = "Cat"
* StringUtils.capitalize("cAt") = "CAt"
* </pre>
*
* @param str the String to capitalize, may be null
* @return the capitalized String, {@code null} if null String input
* @since 2.0
*/
public static String capitalize(String str) {
if(null==str) return null;
if(str.length()==0) return "";
char[] cs=str.toCharArray();
if(cs[0]>96&&cs[0]<123)
cs[0]-=32;
return String.valueOf(cs);
}
public static void main(String[] args) {
System.out.println(StringUtils.join(null,'*'));
System.out.println(StringUtils.join(new String[]{}, '*'));
System.out.println(StringUtils.join(new String[]{null}, '*'));
System.out.println(StringUtils.join(new String[]{"a", "b", "c"}, ';'));
System.out.println(StringUtils.join(new String[]{"a", "b", "c"}, null));
System.out.println(StringUtils.join(new String[]{null, "", "a"}, ';'));
System.out.println(StringUtils.leftPad(null, 100, "*"));
System.out.println(StringUtils.leftPad("", 3, "z"));
System.out.println(StringUtils.leftPad("bat", 3, "z"));
System.out.println(StringUtils.leftPad("bat", 5, "z"));
System.out.println(StringUtils.leftPad("bat", 1, "z"));
System.out.println(StringUtils.leftPad("bat", -1, "z"));
System.out.println(StringUtils.rightPad(null, 100, "*"));
System.out.println(StringUtils.rightPad("", 3, "z"));
System.out.println(StringUtils.rightPad("bat", 3, "z"));
System.out.println(StringUtils.rightPad("bat", 5, "z"));
System.out.println(StringUtils.rightPad("bat", 1, "z"));
System.out.println(StringUtils.rightPad("bat", -1, "z"));
System.out.println(StringUtils.capitalize(null));
System.out.println(StringUtils.capitalize(""));
System.out.println(StringUtils.capitalize("cat"));
System.out.println(StringUtils.capitalize("cAt"));
}
}
哇，楼上辛苦了
先看一下spring的stringutils怎么实现的啊