如何去除字符串前面的空白？

Question

有一个字符串“早上好”。我想删除字符串开始处的边距（可能不是空格，它可能是换行符），并保留边距的中间和后部。 如何做到这一点？

Answer 1

虽然trim()删除前导和尾随空白，只删除前导空格，你需要实现自己的LTRIM方法，如下所示：

public static String ltrim(String s) { 
    int i = 0; 
    while (i < s.length() && Character.isWhitespace(s.charAt(i))) { 
     i++; 
    } 
    return s.substring(i); 
} 

String myString = " whitespace be gone!"; 
String trimmedString = ltrim(myString); 

Answer 2

String b=" This is for test " 
for(int i=0;i<=b.length()-1;i++) 
    { 
    char temp=b.charAt(i); 
    if(temp==' ') 
    { 
     whitespaceNumber++; 
    } 
    } 
    System.out.println("Whitespace number is : "+whitespaceNumber); 

Answer 3

一个正则表达式将很好地工作在这里。当一个或多个空白字符（\\ s +）出现在短语（^）的开头时，请将空白字符替换为空白字符。

private static String trimLeading(String value) { 
    return value != null ? value.replaceFirst("^\\s+", "") : null; 
} 

使用JUnit/hamcrest测试一下：

@Test 
public void test() { 
    assertThat(trimLeading("good morning "), is("good morning ")); 
    assertThat(trimLeading(" good morning "), is("good morning ")); 
    assertThat(trimLeading(" good morning "), is("good morning ")); 
    assertThat(trimLeading("\ngood morning "), is("good morning ")); 
    assertThat(trimLeading("\rgood morning "), is("good morning ")); 
    assertThat(trimLeading("\tgood morning "), is("good morning ")); 
    assertThat(trimLeading(" \t \n \r good morning "), is("good morning ")); 
}