这里有一个并行版本的你有很长的字符串:-)

int width = 100;
String s = "129018";

CharSequence padded = IntStream.range(0,width)
            .parallel()
            .map(i->i-(width-s.length()))
            .map(i->i<0 ? '0' :s.charAt(i))
            .collect(StringBuilder::new, (sb,c)-> sb.append((char)c), (sb1,sb2)->sb1.append(sb2));

填充到10个字符:

String.format("%10s", "foo").replace(' ', '*');
String.format("%-10s", "bar").replace(' ', '*');
String.format("%10s", "longer than 10 chars").replace(' ', '*');

输出:

  *******foo
  bar*******
  longer*than*10*chars

密码字符显示“*”:

String password = "secret123";
String padded = String.format("%"+password.length()+"s", "").replace(' ', '*');

输出与密码字符串长度相同:

  secret123
  *********

Java联机程序，没有花哨的库。

// 6 characters padding example
String pad = "******";
// testcases for 0, 4, 8 characters
String input = "" | "abcd" | "abcdefgh"

左Pad，不要限制

result = pad.substring(Math.min(input.length(),pad.length())) + input;
results: "******" | "**abcd" | "abcdefgh"

右移，不要限制

result = input + pad.substring(Math.min(input.length(),pad.length()));
results: "******" | "abcd**" | "abcdefgh"

左衬垫，限制衬垫长度

result = (pad + input).substring(input.length(), input.length() + pad.length());
results: "******" | "**abcd" | "cdefgh"

右垫，限制垫的长度

result = (input + pad).substring(0, pad.length());
results: "******" | "abcd**" | "abcdef"

在Dzone上找到的

用零填充:

String.format("|%020d|", 93); // prints: |00000000000000000093|

在番石榴中，这很简单:

Strings.padStart("string", 10, ' ');
Strings.padEnd("string", 10, ' ');

很多人都有一些非常有趣的技巧，但我喜欢保持简单，所以我用这个:

public static String padRight(String s, int n, char padding){
    StringBuilder builder = new StringBuilder(s.length() + n);
    builder.append(s);
    for(int i = 0; i < n; i++){
        builder.append(padding);
    }
    return builder.toString();
}

public static String padLeft(String s, int n,  char padding) {
    StringBuilder builder = new StringBuilder(s.length() + n);
    for(int i = 0; i < n; i++){
        builder.append(Character.toString(padding));
    }
    return builder.append(s).toString();
}

public static String pad(String s, int n, char padding){
    StringBuilder pad = new StringBuilder(s.length() + n * 2);
    StringBuilder value = new StringBuilder(n);
    for(int i = 0; i < n; i++){
        pad.append(padding);
    }
    return value.append(pad).append(s).append(pad).toString();
}