java.lang.String 使用遇到的问题点

近日在处理替换String中的字符串的时候，碰到一个问题，代码如下：

String normals= "10+14+16+19+20";

normals = normals.replaceAll("/+", ":");
System.out.println(normals);
//输出的结果是：10+14+16+19+20

normals = normals.replace('+', ':');
System.out.println(normals);
//输出的结果是：10:14:16:19:20

 

String normals= "10+14+16+19+20";

normals = normals.replaceAll("+", ":");
System.out.println(normals);

//系统会提示与此正则表达式错误
Exception in thread "main" java.util.regex.PatternSyntaxException: Dangling meta
character '+' near index 0
+
^
    at java.util.regex.Pattern.error(Unknown Source)
    at java.util.regex.Pattern.sequence(Unknown Source)
    at java.util.regex.Pattern.expr(Unknown Source)
    at java.util.regex.Pattern.compile(Unknown Source)
    at java.util.regex.Pattern.<init>(Unknown Source)
    </init>
    at java.util.regex.Pattern.compile(Unknown Source)
    at java.lang.String.replaceAll(Unknown Source)