你应该看看StringBuilder/StringBuffer，它允许你删除，插入，替换指定偏移量的字符。

你可以轻松地使用String.replace():

String helloWorld = "Hello World!";
String hellWrld = helloWorld.replace("o","");

查看Apache StringUtils:

static String replace(String text, String searchString, String replacement) Replaces all occurrences of a String within another String. static String replace(String text, String searchString, String replacement, int max) Replaces a String with another String inside a larger String, for the first max values of the search String. static String replaceChars(String str, char searchChar, char replaceChar) Replaces all occurrences of a character in a String with another. static String replaceChars(String str, String searchChars, String replaceChars) Replaces multiple characters in a String in one go. static String replaceEach(String text, String[] searchList, String[] replacementList) Replaces all occurrences of Strings within another String. static String replaceEachRepeatedly(String text, String[] searchList, String[] replacementList) Replaces all occurrences of Strings within another String. static String replaceOnce(String text, String searchString, String replacement) Replaces a String with another String inside a larger String, once. static String replacePattern(String source, String regex, String replacement) Replaces each substring of the source String that matches the given regular expression with the given replacement using the Pattern.DOTALL option.

你也可以使用Substring替换现有的字符串:

var str = "abc awwwa";
var Index = str.indexOf('awwwa');
str = str.substring(0, Index);

replace('regex', 'replacement');
replaceAll('regex', 'replacement');

在你的例子中，

String hi = "Hello World!"
String no_o = hi.replaceAll("o", "");

你可以使用

String helloWorld = "Hello World";
String target = "e";
String replacement = "";
String replacedString = helloWorld.replace(target, replacement);

The answer is = Hllo World

或者你可以使用正则表达式

String original = "Java is one of best languages. OOP can be used in Java";
String regexTarget = "\\bJava\\b";
String replacedWord = original.replaceAll(regexTarget, "Python");

The answer is = Python is one of best languages. OOP can be used in Python